Publications by authors named "Martin Palmer"

36 Publications

Exploring Complex Mixtures by Cyclic Ion Mobility High-Resolution Mass Spectrometry: Application Toward Petroleum.

Anal Chem 2021 04 30;93(14):5872-5881. Epub 2021 Mar 30.

International Joint Laboratory-iC2MC: Complex Matrices Molecular Characterization, Total Research and Technology Gonfreville (TRTG), 76700 Harfleur, France.

The in-depth isomeric and isobaric description of ultra-complex organic mixtures remains one of the most challenging analytical tasks. In the last two decades, ion mobility coupled to high-performance mass spectrometry added an additional structural dimension. Despite tremendous instrumental improvements, commercial devices are still limited in ion mobility and mass spectrometric resolving power and struggle to resolve isobaric species and complex isomeric patterns. To overcome these limitations, we explored the capabilities of cyclic ion mobility high-resolution mass spectrometry with special emphasis on petrochemical applications. We could show that quadrupole-selected ion mobility mass spectrometry gives closer insights into the isomeric distribution. In combination with slicing the specific parts of the ion mobility dimension, isobaric interferences could be drastically removed. Collision-induced dissociation (CID) allowed separating structural groups of polycyclic aromatic hydrocarbons and heterocycles (PAH/PASH), deploying up to 10 passes in the cyclic ion mobility device. Finally, we introduce a data processing workflow to resolve the 3.4 mDa SH/C mass split by combining ion mobility and mass spectrometric resolving power. Cyclic ion mobility with the intelligent design of experiments and processing routines will be a powerful approach addressing the isobaric and isomeric complexity of ultra-complex mixtures.
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http://dx.doi.org/10.1021/acs.analchem.1c00222DOI Listing
April 2021

Cyclic Ion Mobility Spectrometry Coupled to High-Resolution Time-of-Flight Mass Spectrometry Equipped with Atmospheric Solid Analysis Probe for the Molecular Characterization of Combustion Particulate Matter.

J Am Soc Mass Spectrom 2021 Jan 25;32(1):206-217. Epub 2020 Nov 25.

Joint Mass Spectrometry Centre/Chair of Analytical Chemistry, University of Rostock, 18059 Rostock, Germany.

Anthropogenic air pollution has a severe impact on climate and human health. The immense molecular complexity and diversity of particulate matter (PM) is a result of primary organic aerosol (POA) as well as secondary organic aerosols (SOAs). In this study, a direct inlet probe (DIP), i.e., atmospheric solids analysis probe (ASAP), with ion mobility high-resolution mass spectrometric detection is applied. Primary particulate matter emissions from three sources were investigated. Furthermore, photochemically aged emissions were analyzed. DIP introduction allowed for a direct analysis with almost no sample preparation and resulted in a complex molecular pattern. This pattern shifted through oxidation processes toward heavier species. For diesel emissions, the fuel's chemical characteristic is partially transferred to the particulate matter by incomplete combustion and characteristic alkylated series were found. Polycyclic aromatic hydrocarbons (PAHs) were identified as major contributors. Ion mobility analysis results in drift time profiles used for structural analysis. The apex position was used to prove structural changes, whereas the full-width-at-half-maximum was used to address the isomeric diversity. With this concept, the dominance of one or a few isomers for certain PAHs could be shown. In contrast, a broad isomeric diversity was found for oxygenated species. For the in-depth specification of fresh and aged spruce emissions, the ion mobility resolving power was almost doubled by allowing for three passes in the circular traveling wave design. The results prove that ASAP coupled with ion mobility spectrometry-mass spectrometry (IMS-MS) serves as a promising analytical approach for tackling the vast molecular complexity of PM.
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http://dx.doi.org/10.1021/jasms.0c00274DOI Listing
January 2021

A comparative study on the physicochemical characteristics of nanoparticles released in vivo from CoCrMo tapers and cement-stem interfaces of total hip replacements.

J Biomed Mater Res B Appl Biomater 2020 11 28;108(8):3311-3322. Epub 2020 Jun 28.

National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, Southampton, UK.

The good biocompatibility and corrosion resistance of the bulk CoCrMo alloy has resulted in it being used in the manufacture of implants and load bearing medical devices. These devices, however, can release wear and corrosion products which differ from the composition of the bulk CoCrMo alloy. The physicochemical characteristics of the particles and the associated in vivo reactivity are dictated by the wear mechanisms and electrochemical conditions at the sites of material loss. Debris released from CoCrMo hip bearings, taper junctions, or cement-stem interfaces can, therefore, have different chemical and morphological characteristics, which provide them with different in vivo toxicities. Here, we propose to assess and compare the characteristics of the particles released in vivo from CoCrMo tapers and cement-stem interfaces which have received less attention compared to debris originating from the hip bearings. The study uses state-of-art characterization techniques to provide a detailed understanding of the size, morphology, composition, and chemistry of the particles liberated from the wear and corrosion flakes from revised hip replacements, with an enzymatic treatment. The phase analyses identified Cr O nanoparticles released from tapers and cement-stem interfaces, whose composition did not vary with origin or particle morphology. The size distributions showed significantly smaller particles were released from the stems, compared to the particles originating from the corresponding tapers. The investigation demonstrates that the tribocorrosive processes occurring at the taper and stem interfaces both result in Cr O nanoparticle formation.
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http://dx.doi.org/10.1002/jbm.b.34667DOI Listing
November 2020

LESA Cyclic Ion Mobility Mass Spectrometry of Intact Proteins from Thin Tissue Sections.

Anal Chem 2020 05 27;92(9):6321-6326. Epub 2020 Apr 27.

Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States.

Liquid extraction surface analysis (LESA) is an ambient surface sampling technique that allows the analysis of intact proteins directly from tissue samples via mass spectrometry. Integration of ion mobility separation to LESA mass spectrometry workflows has shown significant improvements in the signal-to-noise ratios of the resulting protein mass spectra and hence the number of proteins detected. Here, we report the use of a quadrupole-cyclic ion mobility-time-of-flight mass spectrometer (Q-cIM-ToF) for the analysis of proteins from mouse brain and rat kidney tissues sampled via LESA. Among other features, the instrument allows multiple pass cyclic ion mobility separation, with concomitant increase in resolving power. Single-pass experiments enabled the detection of 30 proteins from mouse brain tissue, rising to 44 when quadrupole isolation was employed. In the absence of ion mobility separation, 21 proteins were detected in rat kidney tissue including the abundant α- and β-globin chains from hemoglobin. Single-pass cyclic ion mobility mass spectrometry enabled the detection of 60 additional proteins. Multipass experiments of a narrow / range (/ 870-920) resulted in the detection of 24 proteins (one pass), 37 proteins (two passes) and 54 proteins (three passes), thus demonstrating the benefits of improved mobility resolving power.
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http://dx.doi.org/10.1021/acs.analchem.9b05169DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7304663PMC
May 2020

Application of a novel cyclic ion mobility-mass spectrometer to the analysis of synthetic polymers: A preliminary evaluation.

Rapid Commun Mass Spectrom 2020 Aug 8;34 Suppl 2:e8710. Epub 2020 Feb 8.

Waters Corporation, Wilmslow, UK.

Rationale: Mass spectrometry (MS) is often employed in the characterisation of synthetic polymers. As polymer architecture becomes more complex, ion mobility (IM) is increasingly being coupled with MS to provide an additional dimension of separation, along with structural information. In this study, we explore the use of a novel cyclic ion mobility (cIM) mass spectrometer for the analysis of a co-polymer sample.

Methods: A solution of poly(ethylene glycol)-poly(propylene glycol) random co-polymer (PEG-ran-PPG) was used as a representative polymer sample. The solution was infused into a cIM-enabled quadrupole time-of-flight mass spectrometer. An m/z region of interest, selected using the quadrupole, was passed around the cIM device multiple times. Subsequently, regions of an arrival time distribution were 'sliced' and subjected to tandem mass spectrometric (MS/MS) analysis.

Results: Typical, multiply charged series were observed for the polymer under electrospray ionisation. Multiple passes of the cIM device resulted in the separation of otherwise-overlapping charge states within a narrow m/z window (~3 m/z units), allowing individual selection of ions. These isolated ions were then subjected to post-mobility fragmentation resulting in clean, high-resolution product ion spectra, with a significant reduction in interference.

Conclusions: Scalable IM separation (IMS), brought about by passing ions multiple times around the cIM device, was demonstrated to provide increased IM resolution for ions in the selected m/z window. After multiple passes, deconvoluted high-resolution MS/MS product ion spectra were successfully acquired for ions that previously had interfering overlapping species present.
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http://dx.doi.org/10.1002/rcm.8710DOI Listing
August 2020

High-resolution ion mobility spectrometry-mass spectrometry of isomeric/isobaric ribonucleotide variants.

J Mass Spectrom 2020 Feb 19;55(2):e4465. Epub 2020 Jan 19.

Departments of Chemistry and Biological Sciences, University at Albany, Albany, New York, 12222, USA.

In this report, we explored the benefits of cyclic ion mobility (cIM) mass spectrometry in the analysis of isomeric post-transcriptional modifications of RNA. Standard methyl-cytidine samples were initially utilized to test the ability to correctly distinguish different structures sharing the same elemental composition and thus molecular mass. Analyzed individually, the analytes displayed characteristic arrival times (t ) determined by the different positions of the modifying methyl groups onto the common cytidine scaffold. Analyzed in mixture, the widths of the respective signals resulted in significant overlap that initially prevented their resolution on the t scale. The separation of the four isomers was achieved by increasing the number of passes through the cIM device, which enabled to fully differentiate the characteristic ion mobility behaviors associated with very subtle structural variations. The placement of the cIM device between the mass-selective quadrupole and the time-of-flight analyzer allowed us to perform gas-phase activation of each of these ion populations, which had been first isolated according to a common mass-to-charge ratio and then separated on the basis of different ion mobility behaviors. The observed fragmentation patterns confirmed the structures of the various isomers thus substantiating the benefits of complementing unique t information with specific fragmentation data to reach more stringent analyte identification. These capabilities were further tested by analyzing natural mono-nucleotide mixtures obtained by exonuclease digestion of total RNA extracts. In particular, the combination of cIM separation and post-mobility dissociation allowed us to establish the composition of methyl-cytidine and methyl-adenine components present in the entire transcriptome of HeLa cells. For this reason, we expect that this technique will benefit not only epitranscriptomic studies requiring the determination of identity and expression levels of RNA modifications, but also metabolomics investigations involving the analysis of natural extracts that may possibly contain subsets of isomeric/isobaric species.
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http://dx.doi.org/10.1002/jms.4465DOI Listing
February 2020

Isolation of Crude Oil Peaks Differing by / ∼0.1 via Tandem Mass Spectrometry Using a Cyclic Ion Mobility-Mass Spectrometer.

Anal Chem 2019 11 29;91(22):14268-14274. Epub 2019 Oct 29.

Department of Chemistry , Kyungpook National University , 80 Daehak-ro, Buk-gu , Daegu 41566 , Republic of Korea.

Mass spectrometry is widely used in studying the structures of compounds present in crude oil. In this study, a novel mass spectrometer incorporating a cyclic ion mobility separator was used to obtain tandem mass spectra of crude oil compounds in a narrow mass-to-charge ratio ( window. Isolation of specific peaks was performed by combining quadrupole and ion mobility separation. As a result, peaks differing by an / value of 0.1 could be isolated. Tandem mass spectrometry with collision-induced dissociation was successfully performed to study the chemical structures of the isolated ions. A series of ions ranging from / 374 to / 384, differing by two hydrogen atoms but with the same number of carbons, were isolated and tandem mass spectra were obtained. The higher / precursor ions produced smaller fragment ions; this is explained by the reduced aromaticity owing to an increased number of hydrogen atoms. The ions at / 388 and 374, differing by a CH group, produced very similar fragmentation patterns. Overall, the data obtained from this study clearly demonstrate that the novel cyclic ion mobility-mass spectrometer is a powerful instrument that can provide tandem mass spectra of individual compounds constituting complex mixtures such as crude oils.
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http://dx.doi.org/10.1021/acs.analchem.9b02255DOI Listing
November 2019

Ion-Mobility Spectrometry Can Assign Exact Fucosyl Positions in Glycans and Prevent Misinterpretation of Mass-Spectrometry Data After Gas-Phase Rearrangement.

Angew Chem Int Ed Engl 2019 12 22;58(49):17616-17620. Epub 2019 Oct 22.

Department of Chemical Biology and Drug Discovery, Utrecht University, Universiteitsweg 99, 3584, CG, Utrecht, The Netherlands.

The fucosylation of glycans leads to diverse structures and is associated with many biological and disease processes. The exact determination of fucoside positions by tandem mass spectrometry (MS/MS) is complicated because rearrangements in the gas phase lead to erroneous structural assignments. Here, we demonstrate that the combined use of ion-mobility MS and well-defined synthetic glycan standards can prevent misinterpretation of MS/MS spectra and incorrect structural assignments of fucosylated glycans. We show that fucosyl residues do not migrate to hydroxyl groups but to acetamido moieties of N-acetylneuraminic acid as well as N-acetylglucosamine residues and nucleophilic sites of an anomeric tag, yielding specific isomeric fragment ions. This mechanistic insight enables the characterization of unique IMS arrival-time distributions of the isomers which can be used to accurately determine fucosyl positions in glycans.
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http://dx.doi.org/10.1002/anie.201909623DOI Listing
December 2019

Discrimination of Regioisomeric and Stereoisomeric Saponins from Aesculus hippocastanum Seeds by Ion Mobility Mass Spectrometry.

J Am Soc Mass Spectrom 2019 Nov 26;30(11):2228-2237. Epub 2019 Aug 26.

Organic Synthesis and Mass Spectrometry Laboratory (S2MOs), University of Mons, 23 Place du Parc, 7000, Mons, Belgium.

Modern mass spectrometry methods provide a huge benefit to saponin structural characterization, especially when combined with collision-induced dissociation experiments to obtain a partial description of the saponin (ion) structure. However, the complete description of the structures of these ubiquitous secondary metabolites remain challenging, especially since isomeric saponins presenting small differences are often present in a single extract. As a typical example, the horse chestnut triterpene glycosides, the so-called escins, comprise isomeric saponins containing subtle differences such as cis-trans ethylenic configuration (stereoisomers) of a side chain or distinct positions of an acetyl group (regioisomers) on the aglycone. In the present paper, the coupling of liquid chromatography and ion mobility mass spectrometry has been used to distinguish regioisomeric and stereoisomeric saponins. Ion mobility arrival time distributions (ATDs) were recorded for the stereoisomeric and regioisomeric saponin ions demonstrating that isomeric saponins can be partially separated using ion mobility on a commercially available traveling wave ion mobility (TWIMS) mass spectrometer. Small differences in the ATD can only be monitored when the isomeric saponins are separated with liquid chromatography prior to the IM-MS analysis. However, gas phase separation between stereoisomeric and regioisomeric saponin ions can be successfully realized, without any LC separation, on a cyclic ion mobility-enabled quadrupole time-of-flight (Q-cIM-oaToF) mass spectrometer. The main outcome of the present paper is that the structural analysis of regioisomeric and stereoisomeric natural compounds that represents a real challenge can take huge advantages of ion mobility experiments but only if increased ion mobility resolution is attainable.
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http://dx.doi.org/10.1007/s13361-019-02310-7DOI Listing
November 2019

Structure Determination of Large Isomeric Oligosaccharides of Natural Origin through Multipass and Multistage Cyclic Traveling-Wave Ion Mobility Mass Spectrometry.

Anal Chem 2019 09 3;91(18):12030-12037. Epub 2019 Sep 3.

INRA , UR1268 Biopolymers Interactions Assemblies, La Géraudière B.P. 71627 , F-44316 Nantes , France.

Carbohydrate isomers with identical atomic composition cannot be distinguished by mass spectrometry. By separating the ions according to their conformation in the gas phase, ion mobility (IM) coupled to mass spectrometry is an attractive approach to overcome this issue and extend the limits of mass spectrometry in structural glycosciences. Recent technological developments have significantly increased the resolving power of ion mobility separators. One such instrument features a cyclic traveling-wave IM separator integrated in a quadrupole/time-of-flight mass spectrometer. This system allows for multipass ion separations and for pre-, intra-, and post-IM fragmentation. In the present study, we utilize this system to explore a complex mixture of oligoporphyrans derived from the enzymatic digestion of the cell wall of the red alga . We are able to deduce their complete structure using IM arrival times and the / of specific fragments. This approach was successfully applied for sequencing of oligoporphyrans of up to 1500 Da and included the positioning of the methyl ether and sulfate groups. The structures defined in this study by IM-MS/MS agree with those found in the past but use much more time-consuming analytical approaches. This study also revealed some so far undescribed structures, present at very low abundance. In addition, the results made it possible to compare the abundance of the different isomers released by the enzyme and to draw further conclusions on the specificity of β-porphyranase and more particularly on its accommodation tolerance of anhydro-bridges in subsites. Finally, a separation of two isomers with very similar mobility was obtained after 58 passes around the cIM, with an estimated resolving power of 920 for these triply charged species, confirming the structures attributed to these two isomers.
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http://dx.doi.org/10.1021/acs.analchem.9b03036DOI Listing
September 2019

The effect of matrix interferences on in situ boron isotope analysis by laser ablation multi-collector inductively coupled plasma mass spectrometry.

Rapid Commun Mass Spectrom 2019 May;33(10):959-968

School of Ocean and Earth Science, University of Southampton Waterfront Campus, National Oceanography Centre Southampton, European Way, Southampton, SO14 3ZH, UK.

Rationale: Boron isotope analysis of marine carbonates by laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) offers the potential for rapid sample throughput, and the means to examine micron-scale variations in the δ B signatures of fossil skeletons and shells/tests of marine organisms. Existing studies demonstrate an acceptable level of reproducibility is achievable, but also typically show a level of accuracy outside the limits required by most applications. Here we investigate matrix interference effects as a cause of inaccuracy and imprecision.

Methods: Analyses were performed on a standard format Thermo Scientific Neptune Plus MC-ICP mass spectrometer coupled to a New Wave Research 193 nm ArF laser ablation system. The effects of matrix interference on δ B analysis were investigated through analyses of a set of reference materials with differing B/Ca ratios. Three approaches to correct for matrix-induced effects were trialled: (1) use of matrix-matched standards, (2) utilisation of the relationship between δ B inaccuracy and B/ Ca, B/ ArCa or B/Ca from three reference materials with known δ B values and varying B/Ca ratios, and (3) direct characterisation of the (sloping) interference itself.

Results: Matrix interference from scattered Ca ions on B can impede both the accuracy and the reproducibility of δ B analysis by LA-MC-ICP-MS. Based on analyses of two in-house reference materials, deep sea coral PS69/3181 and inorganic calcite UWC-1, we find approach 2, following the B/Ca relationship, gives the best mean accuracies (within 0.4‰ of solution values) and external reproducibilities (± 0.5‰ 2 SD for PS69/3181). This approach has been applied to analyses of an annual growth cycle of a Siderastrea siderea coral and eight Cibicidoides wuellerstorfi benthic foraminifera. Both coral and foraminifera data match solution MC-ICP-MS analyses within reported uncertainties.

Conclusions: LA-MC-ICP-MS can produce accurate and precise δ B data to a 0.5‰ (2σ) level on <0.3 ng B after correction for Ca interference effects.
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http://dx.doi.org/10.1002/rcm.8432DOI Listing
May 2019

Investigations into the performance of travelling wave enabled conventional and cyclic ion mobility systems to characterise protomers of fluoroquinolone antibiotic residues.

Rapid Commun Mass Spectrom 2019 Jul 18;33 Suppl 2:11-21. Epub 2019 Feb 18.

Waters Corporation, Stamford Avenue, Altrincham Road, Wilmslow, SK9 4AX, UK.

Rationale: Fluoroquinolones (FLQs) have been shown to form protomers with distinctive fragment profiles. Experimental parameters affect protomer formation, impacting observed conventional tandem mass spectrometric (MS/MS) dissociation and multiple reaction monitoring (MRM) transition reproducibility. Collision cross section (CCS) measurement can provide an additional identification metric and improved ion mobility (IM) separation strategies could provide further understanding of fluctuations in fragmentation when using electrospray ionisation (ESI).

Methods: Porcine muscle tissue was fortified with nine fluoroquinolone antibiotics. Extracts were cleaned using QuEChERS dispersive extraction. Separation was achieved via ultra-high-performance liquid chromatography (UHPLC) and analysis performed using positive ion ESI coupled with linear T-wave IM (N and CO drift gas) and cyclic IM-MS (calibrated to perform accurate mass and CCS measurement).

Results: IM-resolved protomeric species have been observed for nine FLQs (uniquely three for danofloxacin). Long-term reproducibility and cross-platform T-wave/cIM studies have demonstrated CCS metric errors <1.5% when compared with a FLQ protomer reference CCS library. When comparing FLQ protomer separation using a standard, linear T-wave IM separator (N /CO ) and using a high-resolution cyclic T-wave device (N ), protomer peak-to-peak resolution ranged between Rs = 1 to Rs = 6 for the IM strategies utilised.

Conclusions: CCS is a reliable cross platform metric; specific FLQ CCS identification fingerprints have been produced, illustrating the potential to compliment MS/MS specificity or provide an alternative identification metric. Using cIM there is opportunity to correlate the erratic nature of protomer formation with the analytical conditions used and to gain further understanding of ionisation/dissociation mechanisms taking place during routine analyses.
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http://dx.doi.org/10.1002/rcm.8371DOI Listing
July 2019

Investigation of nano-sized debris released from CoCrMo secondary interfaces in total hip replacements: Digestion of the flakes.

J Biomed Mater Res B Appl Biomater 2019 02 16;107(2):424-434. Epub 2018 Apr 16.

National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, University Road, Southampton, SO17 1BJ, UK.

The in vivo release of wear debris and corrosion products from the metallic interfaces of total hip replacements is associated with a wide spectrum of adverse body reactions and systemic manifestations. The origin of debris and the electrochemical conditions at the sites of material loss both play a role in determining the physicochemical characteristics of the particles, and thus influence their in vivo reactivity. Debris retrieved from revised CoCrMo tapers and cement-stem interfaces consists of heterogeneous flakes that comprise mechanically mixed metal particles, corrosion products and organic material. Detailed investigation of the size and composition of the metal debris contained within these composites requires the digestion of the flakes to release the small metal particles. Here, we compare alkaline and enzymatic digestion methods that both aim to fragment the flakes and reveal their smallest building blocks. The characterization of debris cleaned with both methods revealed crystalline Cr oxide nanoparticles and clusters. Comparison between the treatments showed that the alkaline method is more efficient in fragmenting the flakes and provided cleaner and generally smaller nanoparticles than exhibited in debris released with the enzymatic treatment. The provision of cleaner nanoparticles from the alkaline method also allows the physicochemical properties of the particles to be more clearly identified. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 424-434, 2019.
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http://dx.doi.org/10.1002/jbm.b.34134DOI Listing
February 2019

Investigation of solubility of carbon dioxide in anhydrous milk fat by lab-scale manometric method.

Food Chem 2017 Dec 1;237:667-676. Epub 2017 Jun 1.

ARC Dairy Innovation Hub, School of Agriculture and Food Sciences, The University of Queensland, QLD 4072, Australia. Electronic address:

This study aims to examine the solubility of CO in anhydrous milk fat (AMF) as functions of partial pressure, temperature, chemical composition and physical state of AMF. AMF was fractionated at 21°C to obtain stearin and olein fractions. The CO solubility was measured using a home-made experimental apparatus based on changes of CO partial pressures. The apparatus was found to be reliable as the measured and theoretical values based on the ideal gas law were comparable. The dissolved CO concentration in AMF increased with an increase in CO partial pressure (0-101kPa). The apparent CO solubility coefficients (molkgPa) in the AMF were 5.75±0.16×10, 3.9±0.19×10 and 1.19±0.14×10 at 35, 24 and 4°C, respectively. Higher liquid oil proportions resulted in higher CO solubility in the AMF. There was insignificant difference in the dissolved CO concentration among the AMF, stearin and olein fractions in their liquid state at 40°C.
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http://dx.doi.org/10.1016/j.foodchem.2017.05.141DOI Listing
December 2017

Effect of solubilised carbon dioxide at low partial pressure on crystallisation behaviour, microstructure and texture of anhydrous milk fat.

Food Res Int 2017 05 28;95:82-90. Epub 2017 Feb 28.

ARC Dairy Innovation Hub, School of Agriculture and Food Sciences, University of Queensland, QLD 4072, Australia.

The crystallisation and melting behaviour, fat polymorphs, microstructure and texture of anhydrous milk fat (AMF) was investigated in the presence of dissolved CO (0-2000ppm) under two crystallising conditions (non-isothermal versus isothermal). CO was found to induce higher onset crystallisation temperature during cooling from 35 to 5°C at 0.5°Cmin. X-ray scattering analysis showed that, in the presence of dissolved CO this rapid crystallisation caused the formation of unstable, α polymorph fat crystals. For milk fat crystallised under isothermal condition at 25°C for 48h, dissolved CO improved solid fat content, slightly depressed melting temperature and exhibited a sharper melting peak. Microstructure of AMF visualised by Polarised light microscopy of crystallised AMF showed that increasing dissolved CO concentration was associated with smaller crystal size and greater crystal number. The bulk properties of the fat appeared to mirror the microstructural differences, in that the texture of CO-treated AMF was harder under isothermal condition but became softer than untreated AMF under cooling condition. The results of this study are of significance in understanding how CO treatment might be used to modulate the crystallisation behaviour of milkfat and thereby the structural development and physical functionality of fat-containing dairy products.
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http://dx.doi.org/10.1016/j.foodres.2017.02.022DOI Listing
May 2017

Damage mechanisms at the cement-implant interface of polished cemented femoral stems.

J Biomed Mater Res B Appl Biomater 2017 10 4;105(7):2027-2033. Epub 2016 Jul 4.

National Centre for Advanced Tribology at Southampton (nCATS), University of Southampton, Highfield, Southampton, UK.

The occurrence of damage on polished femoral stems has been widely reported in the literature, and bone cement has been implicated in a tribocorrosive failure process. However, the mechanisms of cement-mediated damage and the impact of cement formulation on this process are not well understood. In this study, 13 Zimmer CPT polished femoral stems, and the corresponding cement specimens were retrieved at revision surgery and analyzed using high-resolution imaging techniques. Surface damage attributed to tribocorrosion was observed on all stems. Corrosion product, in the form of black flaky surface debris, was observed on the surface of cement specimens; both energy-dispersive X-ray spectroscopy and inductively coupled plasma mass spectrometry(ICP-MS) confirmed the presence of cobalt and chromium, with the ICP-MS showing much higher levels of Cr compared to Co when compared to the original stem material. Agglomerates of ZrO radiopacifier were also identified on the cement surface and, in some cases, showed evidence of abrasive wear; the size of these particles correlated well with elliptical pitting evident on the surfaces of the corresponding stems. This evidence supports the hypothesis that agglomerates of hard radiopacifier particles within the cement may induce a wear-dominated tribocorrosive interaction at the stem-cement interface that damages the surface of polished CoCr femoral stems. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2027-2033, 2017.
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http://dx.doi.org/10.1002/jbm.b.33739DOI Listing
October 2017

Combining density functional theory (DFT) and collision cross-section (CCS) calculations to analyze the gas-phase behaviour of small molecules and their protonation site isomers.

Analyst 2016 Jun;141(13):4044-54

Biomolecular & Analytical Mass Spectrometry group, Department of Chemistry, University of Antwerp, Antwerp, Belgium. and Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK and School of Molecular and Cellular Biology, University of Leeds, LS2 9JT, UK.

Electrospray ion mobility-mass spectrometry (IM-MS) data show that for some small molecules, two (or even more) ions with identical sum formula and mass, but distinct drift times are observed. In spite of showing their own unique and characteristic fragmentation spectra in MS/MS, no configurational or constitutional isomers are found to be present in solution. Instead the observation and separation of such ions appears to be inherent to their gas-phase behaviour during ion mobility experiments. The origin of multiple drift times is thought to be the result of protonation site isomers ('protomers'). Although some important properties of protomers have been highlighted by other studies, correlating the experimental collision cross-sections (CCSs) with calculated values has proven to be a major difficulty. As a model, this study uses the pharmaceutical compound melphalan and a number of related molecules with alternative (gas-phase) protonation sites. Our study combines density functional theory (DFT) calculations with modified MobCal methods (e.g. nitrogen-based Trajectory Method algorithm) for the calculation of theoretical CCS values. Calculated structures can be linked to experimentally observed signals, and a strong correlation is found between the difference of the calculated dipole moments of the protomer pairs and their experimental CCS separation.
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http://dx.doi.org/10.1039/c5an02456kDOI Listing
June 2016

Properties of acid whey as a function of pH and temperature.

J Dairy Sci 2015 Jul 7;98(7):4352-63. Epub 2015 May 7.

Advanced Food Systems Research Unit, College of Health and Biomedicine, Victoria University, Werribee campus, VIC 3030, Australia.

Compositional differences of acid whey (AW) in comparison with other whey types limit its processability and application of conventional membrane processing. Hence, the present study aimed to identify chemical and physical properties of AW solutions as a function of pH (3 to 10.5) at 4 different temperatures (15, 25, 40, or 90°C) to propose appropriate membrane-processing conditions for efficient use of AW streams. The concentration of minerals, mainly calcium and phosphate, and proteins in centrifuged supernatants was significantly lowered with increase in either pH or temperature. Lactic acid content decreased with pH decline and rose at higher temperatures. Calcium appeared to form complexes with phosphates and lactates mainly, which in turn may have induced molecular attractions with the proteins. An increase in pH led to more soluble protein aggregates with large particle sizes. Surface hydrophobicity of these particles increased significantly with temperature up to 40°C and decreased with further heating to 90°C. Surface charge was clearly pH dependent. High lactic acid concentrations appeared to hinder protein aggregation by hydrophobic interactions and may also indirectly influence protein denaturation. Processing conditions such as pH and temperature need to be optimized to manipulate composition, state, and surface characteristics of components of AW systems to achieve an efficient separation and concentration of lactic acid and lactose.
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http://dx.doi.org/10.3168/jds.2015-9435DOI Listing
July 2015

The effects on bronchial epithelial mucociliary cultures of coarse, fine, and ultrafine particulate matter from an underground railway station.

Toxicol Sci 2015 May 10;145(1):98-107. Epub 2015 Feb 10.

*Academic Unit of Clinical and Experimental Sciences, University of Southampton Faculty of Medicine, University Hospital Southampton, Southampton SO16 6YD, United Kingdom, Institute for Life Sciences, Highfield Campus, University of Southampton, Southampton SO17 1BJ, United Kingdom, Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, United Kingdom, NIHR Southampton Respiratory Biomedical Research Unit, University Hospital Southampton, Southampton SO16 6YD, United Kingdom, Centre for Sustainability, Environment, and Health, National Institute for Public Health and the Environment (RIVM), 3720BA Bilthoven, The Netherlands and Institute for Risk Assessment Sciences (IRAS), Utrecht University, 3508TC Utrecht, The Netherlands *Academic Unit of Clinical and Experimental Sciences, University of Southampton Faculty of Medicine, University Hospital Southampton, Southampton SO16 6YD, United Kingdom, Institute for Life Sciences, Highfield Campus, University of Southampton, Southampton SO17 1BJ, United Kingdom, Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, United Kingdom, NIHR Southampton Respiratory Biomedical Research Unit, University Hospital Southampton, Southampton SO16 6YD, United Kingdom, Centre for Sustainability, Environment, and Health, National Institute for Public Health and the Environment (RIVM), 3720BA Bilthoven, The Netherlands and Institute for Risk Assessment Sciences (IRAS), Utrecht University, 3508TC Utrecht, The Netherlands *Academic Unit of Clinical and Experimental Sciences, University of Southampton Faculty of Medicine, University Hospital Southampton, Southampton SO16 6YD, United Kingdom, Institute for Life Sciences, Highfield Campus, University of Southampton, Southampton SO17 1BJ, United Kingdom, Ocean and Earth Science, National Oceanography Centre Southampton, University of Southampton, Southampton SO14 3ZH, United K

We have previously shown that underground railway particulate matter (PM) is rich in iron and other transition metals across coarse (PM10-2.5), fine (PM2.5), and quasi-ultrafine (PM0.18) fractions and is able to generate reactive oxygen species (ROS). However, there is little knowledge of whether the metal-rich nature of such particles exerts toxic effects in mucus-covered airway epithelial cell cultures or whether there is an increased risk posed by the ultrafine fraction. Monolayer and mucociliary air-liquid interface (ALI) cultures of primary bronchial epithelial cells (PBECs) were exposed to size-fractionated underground railway PM (1.1-11.1 µg/cm(2)) and release of lactate dehydrogenase and IL-8 was assayed. ROS generation was measured, and the mechanism of generation studied using desferrioxamine (DFX) and N-acetylcysteine (NAC). Expression of heme oxygenase-1 (HO-1) was determined by RT-qPCR. Particle uptake was studied by transmission electron microscopy. Underground PM increased IL-8 release from PBECs, but this was diminished in mucus-secreting ALI cultures. Fine and ultrafine PM generated a greater level of ROS than coarse PM. ROS generation by ultrafine PM was ameliorated by DFX and NAC, suggesting an iron-dependent mechanism. Despite the presence of mucus, ALI cultures displayed increased HO-1 expression. Intracellular PM was observed within vesicles, mitochondria, and free in the cytosol. The results indicate that, although the mucous layer appears to confer some protection against underground PM, ALI PBECs nonetheless detect PM and mount an antioxidant response. The combination of increased ROS-generating ability of the metal-rich ultrafine fraction and ability of PM to penetrate the mucous layer merits further research.
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http://dx.doi.org/10.1093/toxsci/kfv034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4408962PMC
May 2015

Clinical spectrum of severe leptospirosis in the UK.

JMM Case Rep 2014 Dec 1;1(4):e000003. Epub 2014 Dec 1.

Leptospira Reference Unit, Wye Valley NHS Trust, Hereford HR12ER, UK.

Introduction: Human leptospirosis is a global zoonotic infection with a characteristic biphasic illness and protean clinical manifestations. The majority are mild flu-like infections. The severe forms cause multiorgan damage with a greater predilection to hepatorenal failure.

Case Presentation: We attempted to analyse the clinical presentation of severe leptospirosis and decipher the clinical spectrum within this group by reviewing a series of 15 patients with leptospirosis requiring intensive care support for their management. We noticed complications becoming apparent before antibodies became detectable in the blood in a significant number of patients. This appears to belie the biphasic nature of leptospirosis and raises the question of whether the complications occur during the leptospiraemic phase or the immune phase of the infection. The presence of leptospiral DNA in the blood at this time as detected by a molecular assay strengthened this suspicion. Among the 15 patients with severe leptospirosis, only 3 (20 %) had an overseas travel history and the remaining 12 patients acquired their infection within the UK. Fourteen of the 15 patients had hepatorenal dysfunction, with seven requiring dialysis. Eight of the 15 patients received intravenous ceftriaxone with very good outcomes. Three showed significant clinical improvement after the administration of steroids.

Conclusion: Many patients with severe leptospirosis will have complications on presentation. Molecular testing is now available for early diagnosis, facilitating early interventions. Ceftriaxone has been effective in treating severe leptospirosis. This study reminds clinicians to consider leptospirosis in the differential diagnosis of similar clinical spectra and offers tools for appropriate management.
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http://dx.doi.org/10.1099/jmmcr.0.000003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5415923PMC
December 2014

Crystal structures and morphologies of fractionated milk fat in nanoemulsions.

Food Chem 2015 Mar 6;171:157-67. Epub 2014 Sep 6.

School of Agriculture & Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia. Electronic address:

The triacylglycerol (TAG) crystal structures and morphologies of fractionated milk lipids in nanoemulsions were investigated at 4°C. Droplet size (0.17 versus 1.20 μm), lipid composition (stearin versus olein) and cooling rate (1 versus 10°C min(-1)) had an influence on the structural properties. Five crystal polymorphs (α, β'1, β'2, β1, and β2) were formed with either triple and/or double chain length structures in the solid phases of the emulsified systems. X-ray scattering peak intensities were reduced with the nanoemulsion particles. The internal structure of TAG exhibited stacking of individual lamellar layers (3.8-4.2 nm). Various anisometric shapes of fat nanoparticles were formed due to a highly sharp curvature of the nano-size droplets. The shape of olein nanoparticles was more polyhedral compared to the stearin. TAG crystals arranged in a planar-layered organisation at the slower cooling rate. These differences imply that the nanometric confinement of oil droplets modifies the fat crystal habit.
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http://dx.doi.org/10.1016/j.foodchem.2014.08.113DOI Listing
March 2015

Sonocrystallisation of lactose in concentrated whey.

Ultrason Sonochem 2014 Nov 13;21(6):2117-21. Epub 2014 Apr 13.

Curtin University, School of Public Health, Food Science and Technology Program, Perth, Australia.

Whey concentrated to 32% lactose was sonicated at 30°C in a non-contact approach at flow rates of up to 12L/min. Applied energy density varied from 3 to 16J/mL at a frequency of 20kHz. Sonication of whey initiated the rapid formation of a large number of lactose crystals in response to acoustic cavitation which increased the rate of crystallisation. The rate of sonocrystallisation was greater than stirring for approximately 180min but slowed down between 120 and 180min as the metastable limit was reached. A second treatment with ultrasound at 120min delivering an applied energy density of 4J/mL stimulated further nuclei formation and the rate of crystallisation was maintained for >300min. Yield on the other hand was limited by the solubility of lactose and could not be improved. The crystal size distribution was narrower than that with stirring and the overall crystal size was smaller.
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http://dx.doi.org/10.1016/j.ultsonch.2014.03.031DOI Listing
November 2014

Impact of volcanic ash on anammox communities in deep sea sediments.

Environ Microbiol Rep 2014 Apr 16;6(2):159-66. Epub 2014 Jan 16.

Center for Marine Science, University of North Carolina Wilmington, Wilmington, NC, USA; Department of Biology and Marine Biology, University of North Carolina Wilmington, Wilmington, NC, USA.

Subaerial explosive volcanism contributes substantial amounts of material to the oceans, but little is known about the impact of volcanic ash on sedimentary microbial activity. We have studied anammox communities in deep sea sediments near the volcanically active island of Montserrat, Lesser Antilles. The rates of anammox and denitrification in the sediments were measured using (15)N isotope pairing incubation experiments, while 16S rRNA genes were used to examine anammox community structures. The higher anammox rates were measured in sediment containing the lower accumulation of volcanic ash in the surface sediments, while the lowest activities were found in sediments with the highest ash deposit. 16S rRNA gene analysis revealed the presence of 'Candidatus Scalindua spp.' in the sediments. The lowest diversity of anammox bacteria was observed in the sediments with the highest ash deposit. Overall, this study demonstrates that the deposition of volcanic material in deep sea sediments has negative impacts on activity and diversity of the anammox community. Since anammox may account for up to 79% of N2 production in marine ecosystems, periods of extensive explosive volcanism in Earth history may have had a hitherto unrecognized negative impact on the sedimentary nitrogen removal processes.
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http://dx.doi.org/10.1111/1758-2229.12137DOI Listing
April 2014

Effects of emulsion droplet sizes on the crystallisation of milk fat.

Food Chem 2014 Feb 27;145:725-35. Epub 2013 Aug 27.

School of Agriculture & Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia. Electronic address:

The crystallisation properties of milk fat emulsions containing dairy-based ingredients as functions of emulsion droplet size, cooling rate, and emulsifier type were investigated using a differential scanning calorimeter (DSC). Anhydrous milk fat and its fractions (stearin and olein) were emulsified with whey protein concentrate, sodium caseinate, and Tween80 by homogenisation to produce emulsions in various size ranges (0.13-3.10 μm). Particle size, cooling rate, and types of emulsifier all had an influence on the crystallisation properties of fat in the emulsions. In general, the crystallisation temperature of emulsified fats decreased with decreasing average droplet size and was of an exponent function of size, indicating that the influence of particle size on crystallisation temperature is more pronounced in the sub-micron range. This particle size effect was also verified by electron microscopy.
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http://dx.doi.org/10.1016/j.foodchem.2013.08.072DOI Listing
February 2014

Physicochemical characterization of airborne particulate matter at a mainline underground railway station.

Environ Sci Technol 2013 Apr 2;47(8):3614-22. Epub 2013 Apr 2.

The Brooke Laboratory, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, University Hospital Southampton, Tremona Road, Southampton, SO16 6YD, United Kingdom.

Underground railway stations are known to have elevated particulate matter (PM) loads compared to ambient air. As these particles are derived from metal-rich sources and transition metals may pose a risk to health by virtue of their ability to catalyze generation of reactive oxygen species (ROS), their potential enrichment in underground environments is a source of concern. Compared to coarse (PM10) and fine (PM2.5) particulate fractions of underground railway airborne PM, little is known about the chemistry of the ultrafine (PM0.1) fraction that may contribute significantly to particulate number and surface area concentrations. This study uses inductively coupled plasma mass spectrometry and ion chromatography to compare the elemental composition of size-fractionated underground PM with woodstove, roadwear generator, and road tunnel PM. Underground PM is notably rich in Fe, accounting for greater than 40% by mass of each fraction, and several other transition metals (Cu, Cr, Mn, and Zn) compared to PM from other sources. Importantly, ultrafine underground PM shows similar metal-rich concentrations as the coarse and fine fractions. Scanning electron microscopy revealed that a component of the coarse fraction of underground PM has a morphology indicative of generation by abrasion, absent for fine and ultrafine particulates, which may be derived from high-temperature processes. Furthermore, underground PM generated ROS in a concentration- and size-dependent manner. This study suggests that the potential health effects of exposure to the ultrafine fraction of underground PM warrant further investigation as a consequence of its greater surface area/volume ratio and high metal content.
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http://dx.doi.org/10.1021/es304481mDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3687366PMC
April 2013

Unexpected high pressure effects on the structural properties of condensed whey protein systems.

Biopolymers 2012 Dec;97(12):963-73

School of Applied Sciences, RMIT University, City Campus, Melbourne, Vic. 3001, Australia.

We show that application of high hydrostatic pressure (600 MPa for 15 min) on condensed whey protein (WP) systems (e.g., 80% w/w solids content) results in unexpected structure-function behavior when compared with conventional thermal treatment. Unraveling the relaxation properties in first-order thermodynamic transitions, the manifestation of glass transition phenomena and the preservation of native conformation in condensed preparations were recorded using small-deformation dynamic oscillation in shear, modulated differential scanning calorimetry, and infrared spectroscopy. Informed temperature application results in the formation of continuous networks at the denaturation temperature, which undergo vitrification at subzero temperatures. In contrast, high-pressure-treated WPs resist physicochemical denaturation, hence preserving the native conformation of secondary and tertiary structures. This was rationalized on the basis of a critical concentration threshold where transfer of water molecules to nonpolar residues in the protein interior is minimized because of low moisture content and restricted molecular mobility. The physical state and morphology of these high-solid preparations were further examined by the combined framework of reduced variables and Williams, Landel, and Ferry equation/free volume theory. Theoretical treatment of experimental observations unveils the dynamic range of the mechanical manifestation of the glass transition region in samples subjected to heat or pressure. In addition to preserving native conformation, WPs subjected to high pressure form glassy systems at parity with the structural functionality of the thermally treated counterparts.
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http://dx.doi.org/10.1002/bip.22112DOI Listing
December 2012

Locations of marine animals revealed by carbon isotopes.

Sci Rep 2011 23;1:21. Epub 2011 Jun 23.

School of Ocean and Earth Science, University of Southampton Waterfront Campus, European Way, Southampton SO14 3ZH, UK.

Knowing the distribution of marine animals is central to understanding climatic and other environmental influences on population ecology. This information has proven difficult to gain through capture-based methods biased by capture location. Here we show that marine location can be inferred from animal tissues. As the carbon isotope composition of animal tissues varies with sea surface temperature, marine location can be identified by matching time series of carbon isotopes measured in tissues to sea surface temperature records. Applying this technique to populations of Atlantic salmon (Salmo salar L.) produces isotopically-derived maps of oceanic feeding grounds, consistent with the current understanding of salmon migrations, that additionally reveal geographic segregation in feeding grounds between individual philopatric populations and age-classes. Carbon isotope ratios can be used to identify the location of open ocean feeding grounds for any pelagic animals for which tissue archives and matching records of sea surface temperature are available.
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http://dx.doi.org/10.1038/srep00021DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3216509PMC
August 2013

Effect of ultrasound on the physical and functional properties of reconstituted whey protein powders.

J Dairy Res 2011 May 17;78(2):226-32. Epub 2011 Mar 17.

School of Chemistry/Department of Chemical and Biomolecular Engineering, University of Melbourne, VIC 3010, Australia.

Aqueous solutions of reconstituted whey protein- concentrate (WPC) & isolate (WPI) powders were sonicated at 20 kHz in a batch process for 1-60 min. Sonication at 20 kHz increased the clarity of WPC solutions largely due to the reduction in the size of the suspended insoluble aggregates. The gel strength of these solutions when heated at 80°C for 20 min also increased with sonication, while gelation time and gel syneresis were reduced. These improvements in gel strength were observed across a range of initial pH values, suggesting that the mechanism for gel promotion is different from the well known effects of pH. Examining the microstructure of the whey protein gels indicated a compact network of densely packed whey protein aggregates arising from ultrasound treatment. Comparable changes were not observed with whey protein isolate solutions, which may reflect the absence of larger aggregates in the initial solution or differences in composition.
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http://dx.doi.org/10.1017/S0022029911000070DOI Listing
May 2011

Effects of ultrasound on the thermal and structural characteristics of proteins in reconstituted whey protein concentrate.

Ultrason Sonochem 2011 Sep 31;18(5):951-7. Epub 2010 Dec 31.

School of Chemistry, University of Melbourne, VIC 3010, Australia.

The sonication-induced changes in the structural and thermal properties of proteins in reconstituted whey protein concentrate (WPC) solutions were examined. Differential scanning calorimetry, UV-vis, fluorescence and circular dichroism spectroscopic techniques were used to determine the thermal properties of proteins, measure thiol groups and monitor changes to protein hydrophobicity and secondary structure, respectively. The enthalpy of denaturation decreased when WPC solutions were sonicated for up to 5 min. Prolonged sonication increased the enthalpy of denaturation due to protein aggregation. Sonication did not alter the thiol content but resulted in minor changes to the secondary structure and hydrophobicity of the protein. Overall, the sonication process had little effect on the structure of proteins in WPC solutions which is critical to preserving functional properties during the ultrasonic processing of whey protein based dairy products.
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http://dx.doi.org/10.1016/j.ultsonch.2010.12.016DOI Listing
September 2011

Conservation: the world's religions can help.

Nature 2009 Sep;461(7260):37

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http://dx.doi.org/10.1038/461037bDOI Listing
September 2009