Publications by authors named "Tanja Deckert-Gaudig"

46 Publications

Supramolecular Reorientation During Deposition Onto Metal Surfaces of Quasi-Two-Dimensional Langmuir Monolayers Composed of Bifunctional Amphiphilic, Twisted Perylenes.

Langmuir 2021 Sep 10;37(37):11018-11026. Epub 2021 Sep 10.

Leibniz Institute of Photonic Technology (Leibniz-IPHT), Albert-Einstein-Str. 9, 07745 Jena, Germany.

Supramolecular dye structures, which are often ruled by π-π interactions between planar chromophores, crucially determine the optoelectronic properties of layers and interfaces. Here, we present the interfacial assembly of perylene monoanhydride and monoimide that do not feature a planar chromophore but contain chlorine substituents in the bay positions to yield twisted chromophores and hence modified π-stacking. The assembly of the twisted perylene monoanhydride and monoimide is driven by their amphiphilicity that ensures proper Langmuir layer formation. The shielding of the hydrophilic segment upon attaching an alkyl chain to the imide moiety yielded a more rigid Langmuir layer, even though the degrees of freedom were increased due to this modification. For the characterization of the Langmuir layer's supramolecular structure, the layers were deposited onto glass, silver, and gold substrates via Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) techniques and were investigated with atomic force microscopy and surface-enhanced resonance Raman spectroscopy (SERRS). From the similarity between all SERR spectra of the LS and LB layers, we concluded that the perylenes have changed their orientation upon LB deposition to bind to the silver surface of the SERRS substrate via sulfur atoms. In the Langmuir layer, the perylenes, which are π-stacked with half of the twisted chromophores, must already be inclined and cannot achieve full parallel alignment because of the twisting-induced steric hindrance. However, upon rotation, the energetically most favorable antiparallel aligned structures can be formed and bind to the SERRS substrate. Thus, we present, to the best of our knowledge, the first fabrication of quasi-two-dimensional films from twisted amphiphilic perylene monoimides and their reassembly during LB deposition. The relation between the molecular structure, supramolecular interfacial assembly, and its adoption during adsorption revealed here is crucial for the fabrication of defined functionalizations of metal surfaces, which is key to the development of organic (opto)electronic devices.
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http://dx.doi.org/10.1021/acs.langmuir.1c01525DOI Listing
September 2021

Unveiling the interaction of protein fibrils with gold nanoparticles by plasmon enhanced nano-spectroscopy.

Nanoscale 2021 Sep 2;13(34):14469-14479. Epub 2021 Sep 2.

Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Str. 9, 07745 Jena, Germany.

The development of various degenerative diseases is suggested to be triggered by the uncontrolled organisation and aggregation of proteins into amyloid fibrils. For this reason, there are ongoing efforts to develop novel agents and approaches, including metal nanoparticle-based colloids, that dissolve amyloid structures and prevent pathogenic protein aggregation. In this contribution, the role of gold nanoparticles (AuNPs) in degrading amyloid fibrils of the model protein lysozyme is investigated. The amino acid composition of fibril surfaces before and after the incubation with AuNPs is determined at the single fibril level by exploiting the high spatial resolution and sensitivity provided by tip-enhanced and surface-enhanced Raman spectroscopies. This combined spectroscopic approach allows to reveal the molecular mechanisms driving the interaction between fibrils and AuNPs. Our results provide an important input for the understanding of amyloid fibrils and could have a potential translational impact on the development of strategies for the prevention and treatment of amyloid-related diseases.
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http://dx.doi.org/10.1039/d1nr03190bDOI Listing
September 2021

pH-dependent disintegration of insulin amyloid fibrils monitored with atomic force microscopy and surface-enhanced Raman spectroscopy.

Spectrochim Acta A Mol Biomol Spectrosc 2021 Jul 8;256:119672. Epub 2021 Mar 8.

Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Str. 9, 07745 Jena, Germany; Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich-Schiller-University Jena, Helmholtzweg 4, 07743 Jena, Germany; Institute of Quantum Science and Engineering, Texas A&M University, College Station, TX 77843-4242, USA. Electronic address:

Aggregation of insulin into amyloid fibrils is characterized by the conversion of the native secondary structure of the peptide into an enriched ß-sheet conformation. In vitro, the growth or disintegration of amyloid fibrils can be influenced by various external factors such as pH, temperature etc. While current studies mainly focus on the influence of environmental conditions on the growth process of insulin fibrils, the present study investigates the effect of pH changes on the morphology and secondary structure of mature fibrils. In the experiments, insulin is fibrillated at pH 2.5 and the grown mature fibrils are suspended in pH 4-7 solutions. The obtained structures are analyzed by atomic force microscopy (AFM) and surface-enhanced Raman spectroscopy (SERS). Initially grown mature fibrils from pH 2.5 solutions show a long and intertwined morphology. Increasing the solution pH initiates the gradual disintegration of the filamentous morphology into unordered aggregates. These observations are supported by SERS experiments, where the spectra of the mature fibrils show mainly a β-pleated sheet conformation, while the amide I band region of the amorphous aggregates indicate exclusively α-helix/unordered structures. The results demonstrate that no complex reagent is required for the disintegration of insulin fibrils. Simply regulating the pH of the environment induces local changes in the protonation state within the peptide chains. This effectively disrupts the well-ordered β-sheet structure network based on hydrogen bonds.
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http://dx.doi.org/10.1016/j.saa.2021.119672DOI Listing
July 2021

The impact of episporic modification of on virulence and interaction with phagocytes.

Comput Struct Biotechnol J 2021 20;19:880-896. Epub 2021 Jan 20.

Leibniz Institute for Natural Product Research and Infection Biology - Hans Knöll Institute (HKI), Jena, Germany.

Fungal infections caused by the ancient lineage Mucorales are emerging and increasingly reported in humans. Comprehensive surveys on promising attributes from a multitude of possible virulence factors are limited and so far, focused on and . This study addresses a systematic approach to monitor phagocytosis after physical and enzymatic modification of the outer spore wall of , one of the major causative agents of mucormycosis. Episporic modifications were performed and their consequences on phagocytosis, intracellular survival and virulence by murine alveolar macrophages and in an invertebrate infection model were elucidated. While depletion of lipids did not affect the phagocytosis of both strains, delipidation led to attenuation of LCA strain but appears to be dispensable for infection with LCV strain in the settings used in this study. Combined glucano-proteolytic treatment was necessary to achieve a significant decrease of virulence of the LCV strain in during maintenance of the full potential for spore germination as shown by a novel automated germination assay. Proteolytic and glucanolytic treatments largely increased phagocytosis compared to alive resting and swollen spores. Whilst resting spores barely (1-2%) fuse to lysosomes after invagination in to phagosomes, spore trypsinization led to a 10-fold increase of phagolysosomal fusion as measured by intracellular acidification. This is the first report of a polyphasic measurement of the consequences of episporic modification of a mucormycotic pathogen in spore germination, spore surface ultrastructure, phagocytosis, stimulation of Toll-like receptors (TLRs), phagolysosomal fusion and intracellular acidification, apoptosis, generation of reactive oxygen species (ROS) and virulence.
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http://dx.doi.org/10.1016/j.csbj.2021.01.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7851798PMC
January 2021

Laser spectroscopic technique for direct identification of a single virus I: FASTER CARS.

Proc Natl Acad Sci U S A 2020 11 22;117(45):27820-27824. Epub 2020 Oct 22.

Institute for Quantum Science and Engineering, Texas A&M University, College Station, TX 77843;

From the famous 1918 H1N1 influenza to the present COVID-19 pandemic, the need for improved viral detection techniques is all too apparent. The aim of the present paper is to show that identification of individual virus particles in clinical sample materials quickly and reliably is near at hand. First of all, our team has developed techniques for identification of virions based on a modular atomic force microscopy (AFM). Furthermore, femtosecond adaptive spectroscopic techniques with enhanced resolution via coherent anti-Stokes Raman scattering (FASTER CARS) using tip-enhanced techniques markedly improves the sensitivity [M. O. Scully, , 99, 10994-11001 (2002)].
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http://dx.doi.org/10.1073/pnas.2013169117DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7668096PMC
November 2020

Surface characterization of nanoscale co-crystals enabled through tip enhanced Raman spectroscopy.

Nanoscale 2020 May;12(18):10306-10319

Nanomatériaux pour les Systèmes Sous Sollicitations Extrêmes (NS3E), ISL-CNRS-UNISTRA UMR 3208, French-German Research Institute of Saint-Louis, 5, rue du Général Cassagnou, B.P. 70034, 68301 Saint-Louis, France.

Atomic Force Microscopy coupled with Tip Enhanced Raman Spectroscopy (AFM-TERS) was applied to obtain information about the structure and surface composition of single nano co-crystals. For this purpose, a co-crystalline system consisting of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo-[5.5.0.03,11.05,9]-dodecane (CL-20) and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) in a molar ratio of 2 : 1 (CL-20/HMX) was chosen. CL-20/HMX nano-plates were prepared by spray flash evaporation. To ensure co-crystallinity and nanostructures, powder X-ray diffraction and AFM investigations were performed. The results demonstrate that coherence lengths and particle dimensions are on a similar level though coherence lengths appear shorter than measured particle dimensions. According to this fact, defects inside the nano co-crystals are minimized. The co-crystallinity was additionally proven by confocal Raman spectroscopy. Here, marker bands for pristine CL-20 and HMX were chosen which appear in the CL-20/HMX spectrum in an intensity ratio of ∼2.5 : 1 (CL-20 : HMX). Afterwards surface investigations of single CL-20/HMX nano-plates were performed by AFM-TERS. Due to the surface sensitivity of TERS, these experiments reveal that the ratio of the Raman intensities between CL-20 and HMX inverts at CL-20/HMX nano-plate surfaces. Therefore, it is concluded that nano co-crystal surfaces consist of molecular layers of HMX. A theoretical approximation of the normal coordinates of the investigated marker vibrations supports this conclusion since it can exclude the occurrence of the intensity ratio inversion because of the given orientation between CL-20/HMX nano-plates and the Raman scattering system. Based on this finding, an impact ignition mechanism is proposed, enabling explanation of the close impact sensitivity values of β-HMX and CL-20/HMX.
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http://dx.doi.org/10.1039/d0nr00397bDOI Listing
May 2020

Plasmon induced deprotonation of 2-mercaptopyridine.

Analyst 2020 Mar 4;145(6):2106-2110. Epub 2020 Feb 4.

Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany.

Surface plasmons can provide a novel route to induce and simultaneously monitor selective bond formation and breakage. Here pH-induced protonation, followed by plasmon-induced deprotonation of 2-mercaptopyridine was investigated using surface- and tip-enhanced Raman scattering (SERS and TERS). A large difference in the deprotonation rate between SERS and TERS will be demonstrated and discussed with respect to hot-spot distribution.
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http://dx.doi.org/10.1039/c9an01970gDOI Listing
March 2020

Organic acids, siderophores, enzymes and mechanical pressure for black slate bioweathering with the basidiomycete Schizophyllum commune.

Environ Microbiol 2020 04 31;22(4):1535-1546. Epub 2019 Jul 31.

Friedrich Schiller University, Institute of Microbiology, Microbial Communication, Neugasse 25, D-07743, Jena, Germany.

Although many fungi are known to be able to perform bioweathering of rocks and minerals, little information is available concerning the role of basidiomycetes in this process. The wood-rotting basidiomycete Schizophyllum commune was investigated for its ability to degrade black slate, a rock rich in organic carbon. Mechanical pressure of hyphae and extracellular polymeric substances was investigated for biophysical weathering. A mixed ß1-3/ß1-6 glucan, likely schizophyllan that is well known from S. commune, could be identified on black slate surfaces. Secretion of siderophores and organic acids as biochemical weathering agents was shown. Both may contribute to biochemical weathering in addition to enzymatic functions. Previously, the exoenzyme laccase was believed to attack organic the matter within the black slate, thereby releasing metals from the rock. Here, overexpression of laccase showed enhanced dissolution of quartz phases by etching and pitting. At the same time, the formation of a new secondary mineral phase, whewellite, could be demonstrated. Hence, a more comprehensive understanding of biophysical as well as biochemical weathering by S. commune could be reached and unexpected mechanisms like quartz dissolution linked to shale degradation.
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http://dx.doi.org/10.1111/1462-2920.14749DOI Listing
April 2020

Protein Handshake on the Nanoscale: How Albumin and Hemoglobin Self-Assemble into Nanohybrid Fibers.

ACS Nano 2018 02 12;12(2):1211-1219. Epub 2018 Jan 12.

Chair of Materials Science (CMS), Otto Schott Institute of Materials Research, Faculty of Physics and Astronomy, Friedrich Schiller University Jena , Löbdergraben 32, 07743 Jena, Germany.

Creating and establishing proof of hybrid protein nanofibers (hPNFs), i.e., PNFs that contain more than one protein, is a currently unsolved challenge in bioinspired materials science. Such hPNFs could serve as universal building blocks for the bottom-up preparation of functional materials with bespoke properties. Here, inspired by the protein assemblies occurring in nature, we introduce hPNFs created via a facile self-assembly route and composed of human serum albumin (HSA) and human hemoglobin (HGB) proteins. Our circular dichroism results shed light on the mechanism of the proteins' self-assembly into hybrid nanofibers, which is driven by electrostatic/hydrophobic interactions between similar amino acid sequences (protein handshake) exposed to ethanol-triggered protein denaturation. Based on nanoscale characterization with tip-enhanced Raman spectroscopy (TERS) and immunogold labeling, our results demonstrate the existence and heterogenic nature of the hPNFs and reveal the high HSA/HGB composition ratio, which is attributed to the fast self-assembling kinetics of HSA. The self-assembled hPNFs with a high aspect ratio of over 100 can potentially serve as biocompatible units to create larger bioactive structures, devices, and sensors.
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http://dx.doi.org/10.1021/acsnano.7b07196DOI Listing
February 2018

Tip-enhanced Raman spectroscopy - from early developments to recent advances.

Chem Soc Rev 2017 Jul;46(13):4077-4110

Leibniz Institute of Photonic Technology, Jena, Germany.

An analytical technique operating at the nanoscale must be flexible regarding variable experimental conditions while ideally also being highly specific, extremely sensitive, and spatially confined. In this respect, tip-enhanced Raman scattering (TERS) has been demonstrated to be ideally suited to, e.g., elucidating chemical reaction mechanisms, determining the distribution of components and identifying and localizing specific molecular structures at the nanometre scale. TERS combines the specificity of Raman spectroscopy with the high spatial resolution of scanning probe microscopies by utilizing plasmonic nanostructures to confine the incident electromagnetic field and increase it by many orders of magnitude. Consequently, molecular structure information in the optical near field that is inaccessible to other optical microscopy methods can be obtained. In this general review, the development of this still-young technique, from early experiments to recent achievements concerning inorganic, organic, and biological materials, is addressed. Accordingly, the technical developments necessary for stable and reliable AFM- and STM-based TERS experiments, together with the specific properties of the instruments under different conditions, are reviewed. The review also highlights selected experiments illustrating the capabilities of this emerging technique, the number of users of which has steadily increased since its inception in 2000. Finally, an assessment of the frontiers and new concepts of TERS, which aim towards rendering it a general and widely applicable technique that combines the highest possible lateral resolution and extreme sensitivity, is provided.
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http://dx.doi.org/10.1039/c7cs00209bDOI Listing
July 2017

High resolution spectroscopy reveals fibrillation inhibition pathways of insulin.

Sci Rep 2016 12 23;6:39622. Epub 2016 Dec 23.

Leibniz Institute of Photonic Technology (IPHT), Albert-Einsteinstr. 9, D-07745 Jena, Germany.

Fibril formation implies the conversion of a protein's native secondary structure and is associated with several neurodegenerative diseases. A better understanding of fibrillation inhibition and fibril dissection requires nanoscale molecular characterization of amyloid structures involved. Tip-enhanced Raman scattering (TERS) has already been used to chemically analyze amyloid fibrils on a sub-protein unit basis. Here, TERS in combination with atomic force microscopy (AFM), and conventional Raman spectroscopy characterizes insulin assemblies generated during inhibition and dissection experiments in the presence of benzonitrile, dimethylsulfoxide, quercetin, and β-carotene. The AFM topography indicates formation of filamentous or bead-like insulin self-assemblies. Information on the secondary structure of bulk samples and of single aggregates is obtained from standard Raman and TERS measurements. In particular the high spatial resolution of TERS reveals the surface conformations associated with the specific agents. The insulin aggregates formed under different inhibition and dissection conditions can show a similar morphology but differ in their β-sheet structure content. This suggests different aggregation pathways where the prevention of the β-sheet stacking of the peptide chains plays a major role. The presented approach is not limited to amyloid-related reasearch but can be readily applied to systems requiring extremely surface-sensitive characterization without the need of labels.
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http://dx.doi.org/10.1038/srep39622DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5180225PMC
December 2016

High-resolution Raman Spectroscopy for the Nanostructural Characterization of Explosive Nanodiamond Precursors.

Chemphyschem 2017 Jan 27;18(2):175-178. Epub 2016 Dec 27.

Leibniz Institute of Photonic Technology (IPHT), Albert-Einsteinstr. 9, 07745, Jena, Germany.

The specific attributes of nanodiamonds have attracted increasing interest for electronics or biomedical applications. An efficient synthetic route towards nanodiamonds is via detonation of hexolite (i.e. a mixture of TNT [2,4,6-trinitrotoluene] and RDX [1,3,5-trinitro-1,3,5-triazine]). In particular, detonation of hexolite crystallized by spray flash evaporation (SFE) yields extremely small diamonds (<4 nm). To unravel the detonation mechanism, a structural characterization of the explosives is required but is challenging due to their thermal instability. We demonstrate a combination of conventional Raman spectroscopy and tip-enhanced Raman spectroscopy (TERS) for resolving morphological and structural differences of differently prepared hexolite nanocomposites. The experiments allow for the first time a structural differentiation of individual TNT and RDX crystals and 15-20 nm sized core-shell structures, consequently providing a general approach to investigate the actual composition of mixtures on the nanometer scale.
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http://dx.doi.org/10.1002/cphc.201601276DOI Listing
January 2017

Secondary Structure and Glycosylation of Mucus Glycoproteins by Raman Spectroscopies.

Anal Chem 2016 12 11;88(23):11609-11615. Epub 2016 Nov 11.

Wellcome Trust Centre for Cell-Matrix Research, Faculty of Biology, Medicine and Health, University of Manchester , Manchester M13 9PL, United Kingdom.

The major structural components of protective mucus hydrogels on mucosal surfaces are the secreted polymeric gel-forming mucins. The very high molecular weight and extensive O-glycosylation of gel-forming mucins, which are key to their viscoelastic properties, create problems when studying mucins using conventional biochemical/structural techniques. Thus, key structural information, such as the secondary structure of the various mucin subdomains, and glycosylation patterns along individual molecules, remains to be elucidated. Here, we utilized Raman spectroscopy, Raman optical activity (ROA), circular dichroism (CD), and tip-enhanced Raman spectroscopy (TERS) to study the structure of the secreted polymeric gel-forming mucin MUC5B. ROA indicated that the protein backbone of MUC5B is dominated by unordered conformation, which was found to originate from the heavily glycosylated central mucin domain by isolation of MUC5B O-glycan-rich regions. In sharp contrast, recombinant proteins of the N-terminal region of MUC5B (D1-D2-D'-D3 domains, NT5B), C-terminal region of MUC5B (D4-B-C-CK domains, CT5B) and the Cys-domain (within the central mucin domain of MUC5B) were found to be dominated by the β-sheet. Using these findings, we employed TERS, which combines the chemical specificity of Raman spectroscopy with the spatial resolution of atomic force microscopy to study the secondary structure along 90 nm of an individual MUC5B molecule. Interestingly, the molecule was found to contain a large amount of α-helix/unordered structures and many signatures of glycosylation, pointing to a highly O-glycosylated region on the mucin.
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http://dx.doi.org/10.1021/acs.analchem.6b03095DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5218386PMC
December 2016

Spatially resolved spectroscopic differentiation of hydrophilic and hydrophobic domains on individual insulin amyloid fibrils.

Sci Rep 2016 09 21;6:33575. Epub 2016 Sep 21.

Leibniz Institute of Photonic Technology (IPHT), Albert-Einstein-Str. 9, 07745 Jena, Germany.

The formation of insoluble β-sheet-rich protein structures known as amyloid fibrils is associated with numerous neurodegenerative diseases, such as Alzheimer's and Parkinson's disease. A detailed understanding of the molecular structure of the fibril surface is of interest as the first contact with the physiological environment in vivo and plays a decisive role in biological activity and associated toxicity. Recent studies reveal that the inherent sensitivity and specificity of tip-enhanced Raman scattering (TERS) renders this technique a compelling method for fibril surface analysis at the single-particle level. Here, the reproducibility of TERS is demonstrated, indicating its relevance for detecting molecular variations. Consequently, individual fibrils are systematically investigated at nanometer spatial resolution. Spectral parameters were obtained by band-fitting, particularly focusing on the identification of the secondary structure via the amide III band and the differentiation of hydrophobic and hydrophilic domains on the surface. In addition multivariate data analysis, specifically the N-FINDR procedure, was employed to generate structure-specific maps. The ability of TERS to localize specific structural domains on fibril surfaces shows promise to the development of new fibril dissection strategies and can be generally applied to any (bio)chemical surface when structural variations at the nanometer level are of interest.
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http://dx.doi.org/10.1038/srep33575DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5030623PMC
September 2016

Tip-Enhanced Raman Spectroscopy of Atmospherically Relevant Aerosol Nanoparticles.

Anal Chem 2016 10 21;88(19):9766-9772. Epub 2016 Sep 21.

Institute of Chemical Technologies and Analytics, TU Wien , Getreidemarkt 9, 1060 Vienna, Austria.

Atmospheric aerosol nanoparticles play a major role in many atmospheric processes and in particular in the global climate system. Understanding their formation by homogeneous or heterogeneous nucleation as well as their photochemical aging and atmospheric transformation is of utmost importance to evaluate their impact on atmospheric phenomena. Single particle analysis like tip-enhanced Raman spectroscopy (TERS) opens access to a deeper understanding of these nanoparticles. Atmospherically relevant nanoparticles, formed above a simulated salt lake inside an aerosol smog-chamber, were analyzed using TERS. TERS spectra of 11 nanoparticles were studied in detail. First results of TERS on atmospherically relevant aerosol nanoparticles reveal the presence of inorganic seed particles, a chemical diversity of equally sized particles in the nucleation mode, and chemical transformation during photochemical aging. Therefore, single particle analysis by optical near-field spectroscopy such as TERS of atmospheric nanoparticles will significantly contribute to elucidate atmospheric nucleation, photochemical aging, and chemical transformation processes by uncovering single particle based properties.
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http://dx.doi.org/10.1021/acs.analchem.6b02760DOI Listing
October 2016

Multimodal Spectroscopic Study of Amyloid Fibril Polymorphism.

J Phys Chem B 2016 09 17;120(34):8809-17. Epub 2016 Aug 17.

FOM Institute AMOLF , Science Park 104, 1098 XG Amsterdam, The Netherlands.

Amyloid fibrils are a large class of self-assembled protein aggregates that are formed from unstructured peptides and unfolded proteins. The fibrils are characterized by a universal β-sheet core stabilized by hydrogen bonds, but the molecular structure of the peptide subunits exposed on the fibril surface is variable. Here we show that multimodal spectroscopy using a range of bulk- and surface-sensitive techniques provides a powerful way to dissect variations in the molecular structure of polymorphic amyloid fibrils. As a model system, we use fibrils formed by the milk protein β-lactoglobulin, whose morphology can be tuned by varying the protein concentration during formation. We investigate the differences in the molecular structure and composition between long, straight fibrils versus short, wormlike fibrils. We show using mass spectrometry that the peptide composition of the two fibril types is similar. The overall molecular structure of the fibrils probed with various bulk-sensitive spectroscopic techniques shows a dominant contribution of the β-sheet core but no difference in structure between straight and wormlike fibrils. However, when probing specifically the surface of the fibrils with nanometer resolution using tip-enhanced Raman spectroscopy (TERS), we find that both fibril types exhibit a heterogeneous surface structure with mainly unordered or α-helical structures and that the surface of long, straight fibrils contains markedly more β-sheet structure than the surface of short, wormlike fibrils. This finding is consistent with previous surface-specific vibrational sum-frequency generation (VSFG) spectroscopic results ( VandenAkker et al. J. Am. Chem. Soc. , 2011 , 133 , 18030 - 18033 , DOI: 10.1021/ja206513r ). In conclusion, only advanced vibrational spectroscopic techniques sensitive to surface structure such as TERS and VSFG are able to reveal the difference in structure that underlies the distinct morphology and rigidity of different amyloid fibril polymorphs that have been observed for a large range of food and disease-related proteins.
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http://dx.doi.org/10.1021/acs.jpcb.6b05339DOI Listing
September 2016

Polymorphism of amyloid fibrils formed by a peptide from the yeast prion protein Sup35: AFM and Tip-Enhanced Raman Scattering studies.

Ultramicroscopy 2016 06 30;165:26-33. Epub 2016 Mar 30.

Department of Pharmaceutical Sciences, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE 68198, United States. Electronic address:

Aggregation of prion proteins is the cause of various prion related diseases. The infectious form of prions, amyloid aggregates, exist as multiple strains. The strains are thought to represent structurally different prion protein molecules packed into amyloid aggregates, but the knowledge on the structure of different types of aggregates is limited. Here we report on the use of AFM (Atomic Force Microscopy) and TERS (Tip-Enhanced Raman Scattering) to study morphological heterogeneity and access underlying conformational features of individual amyloid aggregates. Using AFM we identified the morphology of amyloid fibrils formed by the peptide (CGNNQQNY) from the yeast prion protein Sup35 that is critically involved in the aggregation of the full protein. TERS results demonstrate that morphologically different amyloid fibrils are composed of a distinct set of conformations. Fibrils formed at pH 5.6 are composed of a mixture of peptide conformations (β-sheets, random coil and α-helix) while fibrils formed in pH~2 solution primarily have β-sheets. Additionally, peak positions in the amide III region of the TERS spectra suggested that peptides have parallel arrangement of β-sheets for pH~2 fibrils and antiparallel arrangement for fibrils formed at pH 5.6. We also developed a methodology for detailed analysis of the peptide secondary structure by correlating intensity changes of Raman bands in different regions of TERS spectra. Such correlation established that structural composition of peptides is highly localized with large contribution of unordered secondary structures on a fibrillar surface.
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http://dx.doi.org/10.1016/j.ultramic.2016.03.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4879610PMC
June 2016

Detection of Protein Glycosylation Using Tip-Enhanced Raman Scattering.

Anal Chem 2016 Feb 3;88(4):2105-12. Epub 2016 Feb 3.

School of Chemistry and Manchester Institute of Biotechnology, University of Manchester , 131 Princess Street, Manchester, M1 7DN, U.K.

The correct glycosylation of biopharmaceutical glycoproteins and their formulations is essential for them to have the desired therapeutic effect on the patient. It has recently been shown that Raman spectroscopy can be used to quantify the proportion of glycosylated protein from mixtures of native and glycosylated forms of bovine pancreatic ribonuclease (RNase). Here we show the first steps toward not only the detection of glycosylation status but the characterization of glycans themselves from just a few protein molecules at a time using tip-enhanced Raman scattering (TERS). While this technique generates complex data that are very dependent on the protein orientation, with the careful development of combined data preprocessing, univariate and multivariate analysis techniques, we have shown that we can distinguish between the native and glycosylated forms of RNase. Many glycoproteins contain populations of subtly different glycoforms; therefore, with stricter orientation control, we believe this has the potential to lead to further glycan characterization using TERS, which would have use in biopharmaceutical synthesis and formulation research.
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http://dx.doi.org/10.1021/acs.analchem.5b03535DOI Listing
February 2016

Tip-enhanced Raman scattering--Targeting structure-specific surface characterization for biomedical samples.

Adv Drug Deliv Rev 2015 Jul 27;89:42-56. Epub 2015 Jun 27.

Institute for Physical Chemistry and Abbe Center of Photonics, Helmholtzweg 4, Friedrich Schiller-University Jena, D-07743 Jena, Germany; Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, D-07745 Jena, Germany. Electronic address:

Tip-enhanced Raman scattering (TERS) has become a powerful tool for nanoscale structural analysis for several branches of organic, inorganic, and biological chemistry. This highly sensitive technique enables molecular characterization with a lateral resolution far beyond Abbe's diffraction limit and correlates structural and topographic information on a nanometer scale. In this review, the current experimental concepts with respect to their strengths and obstacles are introduced and discussed. A further focus was set to biochemistry comprising applications like nucleic acids, proteins, and microorganisms, thus demonstrating the potential use towards the pharmaceutically relevant challenges where nanometer resolution is required.
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http://dx.doi.org/10.1016/j.addr.2015.06.007DOI Listing
July 2015

Label-free monitoring of plasmonic catalysis on the nanoscale.

Analyst 2015 Jul;140(13):4325-35

Leibniz Institute of Photonic Technology - IPHT, Albert-Einstein-Str. 9, 07745 Jena, Germany.

Plasmonics is the description of specific light matter interactions of metallic structures. In general the size of such structures is well in the nanometer regime and also determines such specific characteristics as color, field confinement etc. Plasmon-induced hot electrons play a vital role in so-called plasmonic catalysis, a field that has recently attracted attention as a new reaction platform. Current reports introduce such nanoscale catalysis as an effective approach to concentrate the energy of visible light and direct it to adsorbed molecules, thereby increasing the chemical reaction rate, and controlling the reaction selectivity. In this review, we present various plasmon-catalyzed reactions specifically monitored with Raman spectroscopy, namely surface-enhanced Raman scattering (SERS), remote SERS (Re-SERS) and tip-enhanced Raman scattering (TERS). These techniques utilize the signal enhancing effect of the metal nanoparticles. However, at the same time they can be used to control the actual reactivity. In the first part, the mechanism of plasmonic catalysis is introduced. Then it is shown how catalytic reactions can be spectroscopically investigated far beyond the diffraction limit using TERS. Finally, the sensitivity of the methods is discussed.
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http://dx.doi.org/10.1039/c5an00630aDOI Listing
July 2015

Nanoscale Heterogeneity of the Molecular Structure of Individual hIAPP Amyloid Fibrils Revealed with Tip-Enhanced Raman Spectroscopy.

Small 2015 Sep 7;11(33):4131-9. Epub 2015 May 7.

FOM Institute AMOLF, Science Park 104, 1098, XG, Amsterdam, The Netherlands.

Type 2 diabetes mellitus is characterized by the pathological deposition of fibrillized protein, known as amyloids. It is thought that oligomers and/or amyloid fibrils formed from human islet amyloid polypeptide (hIAPP or amylin) cause cell death by membrane damage. The molecular structure of hIAPP amyloid fibrils is dominated by β-sheet structure, as probed with conventional infrared and Raman vibrational spectroscopy. However, with these techniques it is not possible to distinguish between the core and the surface structure of the fibrils. Since the fibril surface crucially affects amyloid toxicity, it is essential to know its structure. Here the surface molecular structure and amino acid residue composition of hIAPP fibrils are specifically probed with nanoscale resolution using tip-enhanced Raman spectroscopy (TERS). The fibril surface mainly contains unordered or α-helical structures, in contrast to the β-sheet-rich core. This experimentally validates recent models of hIAPP amyloids based on NMR measurements. Spatial mapping of the surface structure reveals a highly heterogeneous surface structure. Finally, TERS can probe fibrils formed on a lipid interface, which is more representative of amyloids in vivo.
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http://dx.doi.org/10.1002/smll.201500562DOI Listing
September 2015

Surface- and tip-enhanced Raman spectroscopy reveals spin-waves in iron oxide nanoparticles.

Nanoscale 2015 Jun;7(21):9545-51

Institute of Physics, Technische Universität Chemnitz, D-09107 Chemnitz, Germany.

Nanomaterials have the remarkable characteristic of displaying physical properties different from their bulk counterparts. An additional degree of complexity and functionality arises when oxide nanoparticles interact with metallic nanostructures. In this context the Raman spectra due to plasmonic enhancement of iron oxide nanocrystals are here reported showing the activation of spin-waves. Iron oxide nanoparticles on gold and silver tips are found to display a band around 1584 cm(-1) attributed to a spin-wave magnon mode. This magnon mode is not observed for nanoparticles deposited on silicon (111) or on glass substrates. Metal-nanoparticle interaction and the strongly localized electromagnetic field contribute to the appearance of this mode. The localized excitation that generates this mode is confirmed by tip-enhanced Raman spectroscopy (TERS). The appearance of the spin-waves only when the TERS tip is in close proximity to a nanocrystal edge suggests that the coupling of a localized plasmon with spin-waves arises due to broken symmetry at the nanoparticle border and the additional electric field confinement. Beyond phonon confinement effects previously reported in similar systems, this work offers significant insights on the plasmon-assisted generation and detection of spin-waves optically induced.
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http://dx.doi.org/10.1039/c5nr01277eDOI Listing
June 2015

Spatial resolution in Raman spectroscopy.

Faraday Discuss 2015 ;177:9-20

Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany.

This article is intended to set the scope of the meeting, in particular, the high spatial resolution section.
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http://dx.doi.org/10.1039/c5fd90014jDOI Listing
October 2015

Dielectrophoretic positioning of single nanoparticles on atomic force microscope tips for tip-enhanced Raman spectroscopy.

Electrophoresis 2015 May;36(9-10):1142-8

Leibniz Institute of Photonic Technology Jena (IPHT), Jena, Germany.

Tip-enhanced Raman spectroscopy, a combination of Raman spectroscopy and scanning probe microscopy, is a powerful technique to detect the vibrational fingerprint of molecules at the nanometer scale. A metal nanoparticle at the apex of an atomic force microscope tip leads to a large enhancement of the electromagnetic field when illuminated with an appropriate wavelength, resulting in an increased Raman signal. A controlled positioning of individual nanoparticles at the tip would improve the reproducibility of the probes and is quite demanding due to usually serial and labor-intensive approaches. In contrast to commonly used submicron manipulation techniques, dielectrophoresis allows a parallel and scalable production, and provides a novel approach toward reproducible and at the same time affordable tip-enhanced Raman spectroscopy tips. We demonstrate the successful positioning of an individual plasmonic nanoparticle on a commercial atomic force microscope tip by dielectrophoresis followed by experimental proof of the Raman signal enhancing capabilities of such tips.
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http://dx.doi.org/10.1002/elps.201400530DOI Listing
May 2015

A manual and an automatic TERS based virus discrimination.

Nanoscale 2015 Mar;7(10):4545-52

Institute of Physical Chemistry and Abbe Center of Photonics, Friedrich Schiller University, Helmholtzweg 4, 07743 Jena, Germany.

Rapid techniques for virus identification are more relevant today than ever. Conventional virus detection and identification strategies generally rest upon various microbiological methods and genomic approaches, which are not suited for the analysis of single virus particles. In contrast, the highly sensitive spectroscopic technique tip-enhanced Raman spectroscopy (TERS) allows the characterisation of biological nano-structures like virions on a single-particle level. In this study, the feasibility of TERS in combination with chemometrics to discriminate two pathogenic viruses, Varicella-zoster virus (VZV) and Porcine teschovirus (PTV), was investigated. In a first step, chemometric methods transformed the spectral data in such a way that a rapid visual discrimination of the two examined viruses was enabled. In a further step, these methods were utilised to perform an automatic quality rating of the measured spectra. Spectra that passed this test were eventually used to calculate a classification model, through which a successful discrimination of the two viral species based on TERS spectra of single virus particles was also realised with a classification accuracy of 91%.
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http://dx.doi.org/10.1039/c4nr07033jDOI Listing
March 2015

Single molecule level plasmonic catalysis – a dilution study of p-nitrothiophenol on gold dimers.

Chem Commun (Camb) 2015 Feb;51(15):3069-72

Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany.

Surface plasmons on isolated gold dimers can initiate intermolecular reactions of adsorbed p-nitrothiophenol. At the single molecule level when dimerization is not possible an intramolecular reaction can be observed. Experimental evidence indicates that plasmon-induced hot electrons provide the required activation energy.
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http://dx.doi.org/10.1039/c4cc09008jDOI Listing
February 2015

Differences in single and aggregated nanoparticle plasmon spectroscopy.

Phys Chem Chem Phys 2015 Feb 17;17(5):2991-5. Epub 2014 Dec 17.

Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany.

Vibrational spectroscopy usually provides structural information averaged over many molecules. We report a larger peak position variation and reproducibly smaller FWHM of TERS spectra compared to SERS spectra indicating that the number of molecules excited in a TERS experiment is extremely low. Thus, orientational averaging effects are suppressed and micro ensembles are investigated. This is shown for a thiophenol molecule adsorbed on Au nanoplates and nanoparticles.
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http://dx.doi.org/10.1039/c4cp04850dDOI Listing
February 2015

A modified transmission tip-enhanced Raman scattering (TERS) setup provides access to opaque samples.

Appl Spectrosc 2014 ;68(8):916-9

IPHT-Leibniz Institute of Photonic Technology, Albert-Einstein-Str. 9, 07745 Jena, Germany.

The combination of scanning probe microscopy and Raman spectroscopy enables chemical characterization of surfaces at highest spatial resolution. This so-called tip-enhanced Raman scattering (TERS) can be employed for a variety of samples where a label-free characterization or identification of constituents on the nanometer scale is pursued. Present TERS setup geometries are always a compromise for specific dedicated applications and show different advantages and disadvantages: Transmission back-reflection setups, when using immersion objectives with a high numerical aperture, intrinsically provide the highest collection efficiency but cannot be applied for opaque samples. Those samples demand upright setups, at the cost of lower collection efficiency, even though very efficient systems using a parabolic mirror for illumination and collection have been demonstrated. In this contribution it is demonstrated that the incorporation of a dichroic mirror to a transmission TERS setup provides easy access to opaque samples without further modification of the setup.
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http://dx.doi.org/10.1366/13-07419DOI Listing
May 2015

Label-free in vitro visualization and characterization of caveolar bulbs during stimulated re-epithelialization.

Anal Bioanal Chem 2014 Nov 11;406(27):6993-7002. Epub 2014 Jul 11.

, East 42nd Street, New York, NY, 10017, USA.

Tip-enhanced Raman scattering (TERS) was paired with real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) to characterize lipid aggregates during stimulated re-epithelialization using an in vitro wound healing model. In this study, lipid fluctuations in the plasma membrane of epidermal keratinocytes were studied at multiple time points post-wounding. TERS measurements for the first time were also combined with sample analysis after initial wounding and 24 h of wound healing. This enabled simultaneous visualization and characterization of caveolar bulb distribution during wound healing stages, providing noninvasive insight into their associated lipid structure and coating protein, caveolin, in the nanometer range. The combination of Raman spectroscopy and scanning probe microscopy in TERS gives access to topographic and chemical structure information in a single experiment. It is the intrinsic specificity and sensitivity of TERS that enable this discrete detection of cell surface components on the nanometer scale. In contrast with competing biochemical methods, the applied technique does not interfere with the cellular composition, enabling lipid structure analysis without digestion or detergents, and displayed great potential for future biological in vivo studies.
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http://dx.doi.org/10.1007/s00216-014-7998-yDOI Listing
November 2014

Surface characterization of insulin protofilaments and fibril polymorphs using tip-enhanced Raman spectroscopy (TERS).

Biophys J 2014 Jan;106(1):263-71

Department of Chemistry, University at Albany, SUNY, Albany, New York. Electronic address:

Amyloid fibrils are β-sheet-rich protein aggregates that are strongly associated with a variety of neurodegenerative maladies, such as Alzheimer's and Parkinson's diseases. Even if the secondary structure of such fibrils is well characterized, a thorough understanding of their surface organization still remains elusive. Tip-enhanced Raman spectroscopy (TERS) is one of a few techniques that allow the direct characterization of the amino acid composition and the protein secondary structure of the amyloid fibril surface. Herein, we investigated the surfaces of two insulin fibril polymorphs with flat (flat) and left-twisted (twisted) morphology. It was found that the two differ substantially in both amino acid composition and protein secondary structure. For example, the amounts of Tyr, Pro, and His differ, as does the number of carboxyl groups on the respective surfaces, whereas the amounts of Phe and of positively charged amino and imino groups remain similar. In addition, the surface of protofilaments, the precursors of the mature flat and twisted fibrils, was investigated using TERS. The results show substantial differences with respect to the mature fibrils. A correlation of amino acid frequencies and protein secondary structures on the surface of protofilaments and on flat and twisted fibrils allowed us to propose a hypothetical mechanism for the propagation to specific fibril polymorphs. This knowledge can shed a light on the toxicity of amyloids and define the key factors responsible for fibril polymorphism. Finally, this work demonstrates the potential of TERS for the surface characterization of amyloid fibril polymorphs.
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http://dx.doi.org/10.1016/j.bpj.2013.10.040DOI Listing
January 2014
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