Publications by authors named "Jingshu Guo"

32 Publications

Comprehensive Analysis of DNA Adducts Using Data-Independent wSIM/MS Acquisition and wSIM-City.

Anal Chem 2021 Apr 12. Epub 2021 Apr 12.

Masonic Cancer Center, University of Minnesota, Minneapolis 55455, Minnesota, United States.

A novel software has been created to comprehensively characterize covalent modifications of DNA through mass spectral analysis of enzymatically hydrolyzed DNA using the neutral loss of 2'-deoxyribose, a nearly universal MS fragmentation process of protonated 2'-deoxyribonucleosides. These covalent modifications termed DNA adducts form through xenobiotic exposures or by reaction with endogenous electrophiles and can induce mutations during cell division and initiate carcinogenesis. DNA adducts are typically present at trace levels in the human genome, requiring a very sensitive and comprehensive data acquisition and analysis method. Our software, wSIM-City, was created to process mass spectral data acquired by a wide selected ion monitoring (wSIM) with gas-phase fractionation and coupled to wide MS fragmentation. This untargeted approach can detect DNA adducts at trace levels as low as 1.5 adducts per 10 nucleotides. This level of sensitivity is sufficient for comprehensive analysis and characterization of DNA modifications in human specimens.
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http://dx.doi.org/10.1021/acs.analchem.1c00362DOI Listing
April 2021

Hybrid ultrathin-silicon/graphene waveguide photodetector with a loop mirror reflector.

Opt Express 2020 Apr;28(8):10725-10736

Graphene has emerged as a promising solution for on-chip ultrafast photodetection for its advantages of easy integration, high mobility, adjustable chemical potential, and wide operation wavelength range. In order to realize high-performance photodetectors, it is very important to achieve efficient light absorption in the active region. In this work, a compact and high-speed hybrid silicon/graphene photodetector is proposed and demonstrated by utilizing an ultra-thin silicon photonic waveguide integrated with a loop mirror. With this design, the graphene absorption rate for the fundamental mode of TE polarization is improved by ∼5 times compared to that in the conventional hybrid silicon/graphene waveguide with h=220 nm. One can achieve 80% light absorption ratio within the active-region length of only 20 µm for the present silicon/graphene waveguide photodetector at 1550 nm. For the fabricated device, the responsivity is about 25 mA/W under 0.3V bias voltage and the 3-dB bandwidth is about 17 GHz. It is expected to achieve very high bandwidth by introducing high-quality AlO insulator layers and reducing the graphene channel length in the future.
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http://dx.doi.org/10.1364/OE.386103DOI Listing
April 2020

Osteoblastic and anti-osteoclastic activities of strontium-substituted silicocarnotite ceramics: In vitro and studies.

Bioact Mater 2020 Sep 6;5(3):435-446. Epub 2020 Apr 6.

Shanghai Key Laboratory of Orthopaedic Implants, Department of Orthopaedic Surgery, Shanghai Ninth People's Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.

Osteoporosis bone defect is a refractory orthopaedic disease which characterized by impaired bone quality and bone regeneration capacity. Current therapies, including antiosteoporosis drugs and artificial bone grafts, are not always satisfactory. Herein, a strontium-substituted calcium phosphate silicate bioactive ceramic (Sr-CPS) was fabricated. In the present study, the extracts of Sr-CPS were prepared for study and Sr-CPS scaffolds were used for study. The cytocompatibility, osteogenic and osteoclastogenic properties of Sr-CPS extracts were characterized in comparison to CPS. Molecular mechanisms were also evaluated by Western blot. Sr-CPS extracts were found to promote osteogenesis by upregulating Wnt/β-catenin signal pathways and inhibit osteoclastogenesis through downregulating NF-κB signal pathway. micro-CT, histological and histomorphometric observation were conducted after 8 weeks of implantation to evaluate the bone formation using calvarial defects model in ovariectomized rats. Compared with CPS, Sr-CPS significantly promoted critical sized ovariectomy (OVX) calvarial defects healing. Among all the samples, Sr-10 showed the best performance due to a perfect match of bone formation and scaffold degradation rates. Overall, the present study demonstrated that Sr-CPS ceramic can dually modulate both bone formation and resorption, which might be a promising candidate for the reconstruction of osteoporotic bone defect.
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http://dx.doi.org/10.1016/j.bioactmat.2020.03.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7138933PMC
September 2020

Development of a DNA Adductome Mass Spectral Database.

Chem Res Toxicol 2020 04 30;33(4):852-854. Epub 2020 Mar 30.

Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455, United States.

Mass spectrometry-based DNA adductomics is an emerging approach for the human biomonitoring of hazardous chemicals. A mass spectral database of DNA adducts will be created for the scientific community to investigate the associations between chemical exposures, DNA damage, and disease risk.
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http://dx.doi.org/10.1021/acs.chemrestox.0c00031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7197645PMC
April 2020

High-performance silicon-graphene hybrid plasmonic waveguide photodetectors beyond 1.55 μm.

Light Sci Appl 2020 28;9:29. Epub 2020 Feb 28.

1State Key Laboratory for Modern Optical Instrumentation, Zhejiang Provincial Key Laboratory for Sensing Technologies, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Zijingang Campus, 310058 Hangzhou, China.

Graphene has attracted much attention for the realization of high-speed photodetection for silicon photonics over a wide wavelength range. However, the reported fast graphene photodetectors mainly operate in the 1.55 μm wavelength band. In this work, we propose and realize high-performance waveguide photodetectors based on bolometric/photoconductive effects by introducing an ultrathin wide silicon-graphene hybrid plasmonic waveguide, which enables efficient light absorption in graphene at 1.55 μm and beyond. When operating at 2 μm, the present photodetector has a responsivity of ~70 mA/W and a setup-limited 3 dB bandwidth of >20 GHz. When operating at 1.55 μm, the present photodetector also works very well with a broad 3 dB bandwidth of >40 GHz (setup-limited) and a high responsivity of ~0.4 A/W even with a low bias voltage of -0.3 V. This work paves the way for achieving high-responsivity and high-speed silicon-graphene waveguide photodetection in the near/mid-infrared ranges, which has applications in optical communications, nonlinear photonics, and on-chip sensing.
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http://dx.doi.org/10.1038/s41377-020-0263-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7048841PMC
February 2020

Regulating the Behavior of Human Gingival Fibroblasts by sp Domains in Reduced Graphene Oxide.

ACS Biomater Sci Eng 2019 Dec 22;5(12):6414-6424. Epub 2019 Nov 22.

State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China.

Long-term function of dental implants relies on not only stable osseointegration but also strong soft tissue-sealing ability. Ideal soft tissue sealing around implants is an effective protective barrier between the external environment and alveolar bone, preventing the invasion of bacteria that is considered as a vital trigger of irreversible marginal bone loss. Carbon-based materials have been reported to be beneficial to soft tissue sealing, which can be regulated through the hybridization type of carbon atoms (sp or sp), but its internal mechanism is still not clear. In this work, graphene oxide with both sp- and sp-hybridized carbons was electrophoretic deposited on titanium and reduced to regulate the hybridization type of carbon atoms to investigate its effect and possible mechanism on human gingival fibroblasts (HGFs). X-ray photoelectron spectroscopy and Raman mapping test show the increase of sp domain content and the decrease of their size after reduction. Through computer simulation, the possible mechanism of the decrease of sp domain size was proposed. In vitro studies disclose that the HGFs exhibit higher proliferation rate, better adhesion, and migration ability with the increase of sp domains and the decrease of their sizes. It may be due to the amount and size of sp domains that synergistically regulate the amount and properties of adsorbed proteins, thereby influencing the cellular behaviors of HGFs. Our results may offer a different perspective on material designing and academic research to enhance the soft tissue integration of implants.
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http://dx.doi.org/10.1021/acsbiomaterials.9b00497DOI Listing
December 2019

Improved cellular bioactivity by heparin immobilization on polycarbonate film via an aminolysis modification for potential tendon repair.

Int J Biol Macromol 2020 Jan 14;142:835-845. Epub 2019 Oct 14.

State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China. Electronic address:

Tendon repair was an important part during tendon to bone healing. In the present study, heparin molecules were immobilized on the aminolyzed PCL surface to improve the cellular bioactivity for potential tendon repair. The effects of heparin immobilization on protein adsorption behavior and cellular bioactivity of NIH3T3 and ATDC5 cells were investigated. The results were shown as follows.
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http://dx.doi.org/10.1016/j.ijbiomac.2019.09.136DOI Listing
January 2020

Methods and Challenges for Computational Data Analysis for DNA Adductomics.

Chem Res Toxicol 2019 11 6;32(11):2156-2168. Epub 2019 Nov 6.

Masonic Cancer Center , University of Minnesota , Minneapolis , Minnesota 55455 , United States.

Frequent exposure to chemicals in the environment, diet, and endogenous electrophiles leads to chemical modification of DNA and the formation of DNA adducts. Some DNA adducts can induce mutations during cell division and, when occurring in critical regions of the genome, can lead to the onset of disease, including cancer. The targeted analysis of DNA adducts over the past 30 years has revealed that the human genome contains many types of DNA damages. However, a long-standing limitation in conducting DNA adduct measurements has been the inability to screen for the total complement of DNA adducts derived from a wide range of chemicals in a single assay. With the advancement of high-resolution mass spectrometry (MS) instrumentation and new scanning technologies, nontargeted "omics" approaches employing data-dependent acquisition and data-independent acquisition methods have been established to simultaneously screen for multiple DNA adducts, a technique known as DNA adductomics. However, notable challenges in data processing must be overcome for DNA adductomics to become a mature technology. DNA adducts occur at low abundance in humans, and current softwares do not reliably detect them when using common MS data acquisition methods. In this perspective, we discuss contemporary computational tools developed for feature finding of MS data widely utilized in the disciplines of proteomics and metabolomics and highlight their limitations for conducting nontargeted DNA-adduct biomarker discovery. Improvements to existing MS data processing software and new algorithms for adduct detection are needed to develop DNA adductomics into a powerful tool for the nontargeted identification of potential cancer-causing agents.
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http://dx.doi.org/10.1021/acs.chemrestox.9b00196DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7127864PMC
November 2019

Quantitation of Lipid Peroxidation Product DNA Adducts in Human Prostate by Tandem Mass Spectrometry: A Method That Mitigates Artifacts.

Chem Res Toxicol 2019 09 16;32(9):1850-1862. Epub 2019 Aug 16.

Reactive oxygen species (ROS) and chronic inflammation contribute to DNA damage of many organs, including the prostate. ROS cause oxidative damage to biomolecules, such as lipids, proteins, and nucleic acids, resulting in the formation of toxic and mutagenic intermediates. Lipid peroxidation (LPO) products covalently adduct to DNA and can lead to mutations. The levels of LPO DNA adducts reported in humans range widely. However, a large proportion of the DNA adducts may be attributed to artifact formation during the steps of isolation and nuclease digestion of DNA. We established a method that mitigates artifacts for most LPO adducts during the processing of DNA. We have applied this methodology to measure LPO DNA adducts in the genome of prostate cancer patients, employing ultrahigh-performance liquid chromatography electrospray ionization ion trap multistage mass spectrometry. Our preliminary data show that DNA adducts of acrolein, 6-hydroxy-1,-propano-2'-deoxyguanosine (6-OH-PdG) and 8-hydroxy-1,-propano-2'-deoxyguanosine (8-OH-PdG) (4-20 adducts per 10 nucleotides) are more prominent than etheno (ε) adducts (<0.5 adducts per 10 nucleotides). This analytical methodology will be used to examine the correlation between oxidative stress, inflammation, and LPO adduct levels in patients with benign prostatic hyperplasia and prostate cancer.
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http://dx.doi.org/10.1021/acs.chemrestox.9b00181DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6746595PMC
September 2019

High strength polymer/silicon nitride composites for dental restorations.

Dent Mater 2019 09 12;35(9):1254-1263. Epub 2019 Jun 12.

State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China. Electronic address:

Objectives: To fabricate polymer-infiltrated silicon nitride composite (PISNC) and evaluate the potential of PISNC in dental application.

Methods: Porous silicon nitride (SiN) ceramics were fabricated through gelcasting and pressureless sintering. Polymer infiltrating was carried out then and composites were obtained after curing of polymer. Flexural strength and microstructures of porous ceramic scaffolds and polymer-infiltrated composites were obtained by three-point bending and SEM, respectively. Phase distributions of polymer-infiltrated ceramics were observed by EDS. Human gingival fibroblast cells (HGFs) were used to evaluate the cytocompatibility and IL-6 release. The cell morphology were observed by SEM. The amount of released IL-6 was investigated using ELISA test system.

Results: Porosity and mechanical strength of porous ceramics ranged from 45.1 to 49.3% and 171.8-262.3MPa, respectively. The bicontinuous structure of polymer-infiltrated composites possessed them with excellent mechanical properties. Porosity and mechanical strength of polymer-infiltrated SiN composites ranged from 1.94 to 2.28% and 273-385.3MPa, respectively. Additionally, the PISNC enhanced the initial adhesion and spreading activity of HGFs compared with PMMA. The PISNC showed similar IL-6 release performance with PMMA samples.

Significances: The PISNC is a promising candidate for dental restorations and high-load medical applications.
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http://dx.doi.org/10.1016/j.dental.2019.05.022DOI Listing
September 2019

Emerging Technologies in Mass Spectrometry-Based DNA Adductomics.

High Throughput 2019 May 14;8(2). Epub 2019 May 14.

Masonic Cancer Center and Department of Medicinal Chemistry, University of Minnesota, 2231 6th St. SE, Minneapolis, MI 55455, USA.

The measurement of DNA adducts, the covalent modifications of DNA upon the exposure to the environmental and dietary genotoxicants and endogenously produced electrophiles, provides molecular evidence for DNA damage. With the recent improvements in the sensitivity and scanning speed of mass spectrometry (MS) instrumentation, particularly high-resolution MS, it is now feasible to screen for the totality of DNA damage in the human genome through DNA adductomics approaches. Several MS platforms have been used in DNA adductomic analysis, each of which has its strengths and limitations. The loss of 2'-deoxyribose from the modified nucleoside upon collision-induced dissociation is the main transition feature utilized in the screening of DNA adducts. Several advanced data-dependent and data-independent scanning techniques originated from proteomics and metabolomics have been tailored for DNA adductomics. The field of DNA adductomics is an emerging technology in human exposure assessment. As the analytical technology matures and bioinformatics tools become available for analysis of the MS data, DNA adductomics can advance our understanding about the role of chemical exposures in DNA damage and disease risk.
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http://dx.doi.org/10.3390/ht8020013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6630665PMC
May 2019

Targeted and Untargeted Detection of DNA Adducts of Aromatic Amine Carcinogens in Human Bladder by Ultra-Performance Liquid Chromatography-High-Resolution Mass Spectrometry.

Chem Res Toxicol 2018 12 19;31(12):1382-1397. Epub 2018 Nov 19.

Department of Pharmacological Sciences , Stony Brook University , Stony Brook , New York 11794 , United States.

Epidemiological studies have linked aromatic amines (AAs) from tobacco smoke and some occupational exposures with bladder cancer risk. Several epidemiological studies have also reported a plausible role for structurally related heterocyclic aromatic amines present in tobacco smoke or formed in cooked meats with bladder cancer risk. DNA adduct formation is an initial biochemical event in bladder carcinogenesis. We examined paired fresh-frozen (FR) and formalin-fixed paraffin-embedded (FFPE) nontumor bladder tissues from 41 bladder cancer patients for DNA adducts of 4-aminobiphenyl (4-ABP), a bladder carcinogen present in tobacco smoke, and 2-amino-9 H-pyrido[2,3- b]indole, 2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine and 2-amino-3,8-dimethylimidazo[4,5- f]quinoxaline, possible human carcinogens, which occur in tobacco smoke and cooked meats. These chemicals are present in urine of tobacco smokers or omnivores. Targeted DNA adduct measurements were done by ultra-performance liquid chromatography-electrospray ionization multistage hybrid Orbitrap MS. N-(2'-Deoxyguanosin-8-yl)-4-ABP ( N-(dG-C8)-4-ABP) was the sole adduct detected in FR and FFPE bladder tissues. Twelve subjects (29%) had N-(dG-C8)-4-ABP levels above the limit of quantification, ranging from 1.4 to 33.8 adducts per 10 nucleotides (nt). DNA adducts of other human AA bladder carcinogens, including 2-naphthylamine (2-NA), 2-methylaniline (2-MA), 2,6-dimethylaniline (2,6-DMA), and lipid peroxidation (LPO) adducts, were screened for in bladder tissue, by our untargeted data-independent adductomics method, termed wide-selected ion monitoring (wide-SIM)/MS. Wide-SIM/MS successfully detected N-(dG-C8)-4-ABP, N-(2'-deoxyadenosin-8-yl)-4-ABP and the presumed hydrazo linked adduct, N-(2'-deoxyguanosin- N-yl)-4-ABP, and several LPO adducts in bladder DNA. Wide-SIM/MS detected multiple DNA adducts of 2-NA, 2-MA, and, 2,6-DMA, when calf thymus DNA was modified with reactive intermediates of these carcinogens. However, these AA-adducts were below the limit of detection in unspiked human bladder DNA (<1 adduct per 10 nt). Wide-SIM/MS can screen for many types of DNA adducts formed with exogenous and endogenous electrophiles and will be employed to identify DNA adducts of other chemicals that may contribute to the etiology of bladder cancer.
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http://dx.doi.org/10.1021/acs.chemrestox.8b00268DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6424598PMC
December 2018

Perovskite light-emitting diodes based on spontaneously formed submicrometre-scale structures.

Nature 2018 10 10;562(7726):249-253. Epub 2018 Oct 10.

Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), Nanjing Tech University (NanjingTech), Nanjing, China.

Light-emitting diodes (LEDs), which convert electricity to light, are widely used in modern society-for example, in lighting, flat-panel displays, medical devices and many other situations. Generally, the efficiency of LEDs is limited by nonradiative recombination (whereby charge carriers recombine without releasing photons) and light trapping. In planar LEDs, such as organic LEDs, around 70 to 80 per cent of the light generated from the emitters is trapped in the device, leaving considerable opportunity for improvements in efficiency. Many methods, including the use of diffraction gratings, low-index grids and buckling patterns, have been used to extract the light trapped in LEDs. However, these methods usually involve complicated fabrication processes and can distort the light-output spectrum and directionality. Here we demonstrate efficient and high-brightness electroluminescence from solution-processed perovskites that spontaneously form submicrometre-scale structures, which can efficiently extract light from the device and retain wavelength- and viewing-angle-independent electroluminescence. These perovskites are formed simply by introducing amino-acid additives into the perovskite precursor solutions. Moreover, the additives can effectively passivate perovskite surface defects and reduce nonradiative recombination. Perovskite LEDs with a peak external quantum efficiency of 20.7 per cent (at a current density of 18 milliamperes per square centimetre) and an energy-conversion efficiency of 12 per cent (at a high current density of 100 milliamperes per square centimetre) can be achieved-values that approach those of the best-performing organic LEDs.
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http://dx.doi.org/10.1038/s41586-018-0576-2DOI Listing
October 2018

DNA adducts: Formation, biological effects, and new biospecimens for mass spectrometric measurements in humans.

Mass Spectrom Rev 2020 03 11;39(1-2):55-82. Epub 2018 Jun 11.

Masonic Cancer Center and Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN.

Hazardous chemicals in the environment and diet or their electrophilic metabolites can form adducts with genomic DNA, which can lead to mutations and the initiation of cancer. In addition, reactive intermediates can be generated in the body through oxidative stress and damage the genome. The identification and measurement of DNA adducts are required for understanding exposure and the causal role of a genotoxic chemical in cancer risk. Over the past three decades, P-postlabeling, immunoassays, gas chromatography/mass spectrometry, and liquid chromatography/mass spectrometry (LC/MS) methods have been established to assess exposures to chemicals through measurements of DNA adducts. It is now possible to measure some DNA adducts in human biopsy samples, by LC/MS, with as little as several milligrams of tissue. In this review article, we highlight the formation and biological effects of DNA adducts, and highlight our advances in human biomonitoring by mass spectrometric analysis of formalin-fixed paraffin-embedded tissues, untapped biospecimens for carcinogen DNA adduct biomarker research.
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http://dx.doi.org/10.1002/mas.21570DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6289887PMC
March 2020

Formalin-Fixed Paraffin-Embedded Tissues-An Untapped Biospecimen for Biomonitoring DNA Adducts by Mass Spectrometry.

Toxics 2018 Jun 1;6(2). Epub 2018 Jun 1.

Masonic Cancer Center and Department of Medicinal Chemistry, University of Minnesota, 2231 6th St. SE, Minneapolis, MN 55455, USA.

The measurement of DNA adducts provides important information about human exposure to genotoxic chemicals and can be employed to elucidate mechanisms of DNA damage and repair. DNA adducts can serve as biomarkers for interspecies comparisons of the biologically effective dose of procarcinogens and permit extrapolation of genotoxicity data from animal studies for human risk assessment. One major challenge in DNA adduct biomarker research is the paucity of fresh frozen biopsy samples available for study. However, archived formalin-fixed paraffin-embedded (FFPE) tissues with clinical diagnosis of disease are often available. We have established robust methods to recover DNA free of crosslinks from FFPE tissues under mild conditions which permit quantitative measurements of DNA adducts by liquid chromatography-mass spectrometry. The technology is versatile and can be employed to screen for DNA adducts formed with a wide range of environmental and dietary carcinogens, some of which were retrieved from section-cuts of FFPE blocks stored at ambient temperature for up to nine years. The ability to retrospectively analyze FFPE tissues for DNA adducts for which there is clinical diagnosis of disease opens a previously untapped source of biospecimens for molecular epidemiology studies that seek to assess the causal role of environmental chemicals in cancer etiology.
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http://dx.doi.org/10.3390/toxics6020030DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6027047PMC
June 2018

Bioactive calcium phosphate silicate ceramic surface-modified PLGA for tendon-to-bone healing.

Colloids Surf B Biointerfaces 2018 Apr 4;164:388-395. Epub 2018 Feb 4.

State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramic, Chinese Academy of Science, Shanghai, 200050, China. Electronic address:

Due to the dissimilar features between the tendon and bone, tendon to bone healing is the most challenging problems in sports medicine. In the present work, a novel bioactive calcium phosphate silicate ceramic (CPS) was coated on the surface of PLGA films using electron beam evaporation (EBE) technique to prepare a tailorable composite film with layered chemical composition similar to tendon-bone interface. The physicochemical behaviors of the CPS-PLGA composite films were characterized and the cytocompatibility were also investigated. It was found that the CPS-modified samples exhibited a significantly improved hydrophilicity and a more negative zeta potential. Cell culture results showed that the CPS-modified samples were beneficial to the attachment and proliferation of rBMSCs and NIH3T3 cells. CPS-modified samples also showed an improved osteogenic activity. The results suggested that CPS-modified PLGA films have great potentials for tendon-bone healing.
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http://dx.doi.org/10.1016/j.colsurfb.2018.02.001DOI Listing
April 2018

Data-Independent Mass Spectrometry Approach for Screening and Identification of DNA Adducts.

Anal Chem 2017 11 18;89(21):11728-11736. Epub 2017 Oct 18.

Masonic Cancer Center and ∥Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota , 2231 Sixth Street SE, Minneapolis, Minnesota 55455, United States.

Long-term exposures to environmental toxicants and endogenous electrophiles are causative factors for human diseases including cancer. DNA adducts reflect the internal exposure to genotoxicants and can serve as biomarkers for risk assessment. Liquid chromatography-multistage mass spectrometry (LC-MS) is the most common method for biomonitoring DNA adducts, generally targeting single exposures and measuring up to several adducts. However, the data often provide limited evidence for a role of a chemical in the etiology of cancer. An "untargeted" method is required that captures global exposures to chemicals, by simultaneously detecting their DNA adducts in the genome; some of which may induce cancer-causing mutations. We established a wide selected ion monitoring tandem mass spectrometry (wide-SIM/MS) screening method utilizing ultraperformance-LC nanoelectrospray ionization Orbitrap MS with online trapping to enrich bulky, nonpolar adducts. Wide-SIM scan events are followed by MS scans to screen for modified nucleosides by coeluting peaks containing precursor and fragment ions differing by -116.0473 Da, attributed to the neutral loss of deoxyribose. Wide-SIM/MS was shown to be superior in sensitivity, specificity, and breadth of adduct coverage to other tested adductomic methods with detection possible at adduct levels as low as 4 per 10 nucleotides. Wide-SIM/MS data can be analyzed in a "targeted" fashion by generation of extracted ion chromatograms or in an "untargeted" fashion where a chromatographic peak-picking algorithm can be used to detect putative DNA adducts. Wide-SIM/MS successfully detected DNA adducts, derived from chemicals in the diet and traditional medicines and from lipid peroxidation products, in human prostate and renal specimens.
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http://dx.doi.org/10.1021/acs.analchem.7b03208DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5727898PMC
November 2017

Enhanced light absorption in waveguide Schottky photodetector integrated with ultrathin metal/silicide stripe.

Opt Express 2017 May;25(9):10057-10069

We investigate the light absorption enhancement in waveguide Schottky photodetector integrated with ultrathin metal/silicide stripe, which can provide high internal quantum efficiency. By using aab0-quasi-TE hybrid modes for the first time, a high absorptance of 95.6% is achieved in 5 nm thick Au stripe with area of only 0.14 μm2, without using resonance structure. In theory, the responsivity, dark current, and 3dB bandwidth of the corresponding device are 0.146 A/W, 8.03 nA, and 88 GHz, respectively. For most silicides, the quasi-TM mode should be used in this device, and an optimized PtSi device has a responsivity of 0.71 A/W and a dark current of 35.9 μA.
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http://dx.doi.org/10.1364/OE.25.010057DOI Listing
May 2017

Biomonitoring DNA Adducts of Cooked Meat Carcinogens in Human Prostate by Nano Liquid Chromatography-High Resolution Tandem Mass Spectrometry: Identification of 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine DNA Adduct.

Anal Chem 2016 12 1;88(24):12508-12515. Epub 2016 Dec 1.

Masonic Cancer Center and ‡Department of Medicinal Chemistry, University of Minnesota , 2231 Sixth Street SE, Minneapolis, Minnesota 55455, United States.

Epidemiologic studies have reported an association between frequent consumption of well-done cooked meats and prostate cancer risk. However, unambiguous physiochemical markers of DNA damage from carcinogens derived from cooked meats, such as DNA adducts, have not been identified in human samples to support this paradigm. We have developed a highly sensitive nano-LC-Orbitrap MS method to measure DNA adducts of several carcinogens originating from well-done cooked meats, tobacco smoke, and environmental pollution, including 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-9H-pyrido[2,3-b]indole (AαC), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), benzo[a]pyrene (B[a]P), and 4-aminobiphenyl (4-ABP). The limit of quantification (LOQ) of the major deoxyguanosine (dG) adducts of these carcinogens ranged between 1.3 and 2.2 adducts per 10 nucleotides per 2.5 μg of DNA assayed. The DNA adduct of PhIP, N-(deoxyguanosin-8-yl)-PhIP (dG-C8-PhIP) was identified in 11 out of 35 patients, at levels ranging from 2 to 120 adducts per 10 nucleotides. The dG-C8 adducts of AαC and MeIQx, and the B[a]P adduct, 10-(deoxyguanosin-N -yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (dG-N -B[a]PDE) were not detected in any specimen, whereas N-(deoxyguanosin-8-yl)-4-ABP (dG-C8-4-ABP) was identified in one subject (30 adducts per 10 nucleotides). PhIP-DNA adducts also were recovered quantitatively from formalin fixed paraffin embedded (FFPE) tissues, signifying FFPE tissues can serve as biospecimens for carcinogen DNA adduct biomarker research. Our biomarker data provide support to the epidemiological observations implicating PhIP, one of the most mass-abundant heterocyclic aromatic amines formed in well-done cooked meats, as a DNA-damaging agent that may contribute to the etiology of prostate cancer.
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http://dx.doi.org/10.1021/acs.analchem.6b04157DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5545982PMC
December 2016

Passivated Single-Crystalline CHNHPbI Nanowire Photodetector with High Detectivity and Polarization Sensitivity.

Nano Lett 2016 12 4;16(12):7446-7454. Epub 2016 Nov 4.

Wuhan National Laboratory for Optoelectronics (WNLO) and School of Optical and Electronic Information, Huazhong University of Science and Technology (HUST) , Wuhan 430074, China.

Photodetectors convert light signals into current or voltage outputs and are widely used for imaging, sensing, and spectroscopy. Perovskite-based photodetectors have shown high sensitivity and fast response due to the unprecedented low recombination loss in this solution processed semiconductor. Among various types of CHNHPbI morphology (film, single crystal, nanowire), single-crystalline CHNHPbI nanowires are particularly interesting for photodetection because of their reduced grain boundary, morphological anisotropy, and excellent mechanical flexibility. The concomitant disadvantage associated with the CHNHPbI nanowire photodetectors is their large surface area, which catalyzes carrier recombination and material decomposition, thus significantly degrading device performance and stability. Here we solved this key problem by introducing oleic acid soaking to passivate surface defects of CHNHPbI nanowires, which leads to a device with much improved stability and unprecedented sensitivity (measured detectivity of 2 × 10 Jones). By taking advantage of their one-dimensional geometry, we also showcased, for the first time, the linear dichroic photodetection of our CHNHPbI nanowire photodetector.
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http://dx.doi.org/10.1021/acs.nanolett.6b03119DOI Listing
December 2016

Human Biomonitoring of DNA Adducts by Ion Trap Multistage Mass Spectrometry.

Curr Protoc Nucleic Acid Chem 2016 09 1;66:7.24.1-7.24.25. Epub 2016 Sep 1.

Masonic Cancer Center and Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, Minneapolis, Minnesota.

Humans are continuously exposed to hazardous chemicals in the environment. These chemicals or their electrophilic metabolites can form adducts with genomic DNA, which can lead to mutations and the initiation of cancer. The identification of DNA adducts is required for understanding exposure and the etiological role of a genotoxic chemical in cancer risk. The analytical chemist is confronted with a great challenge because the levels of DNA adducts generally occur at <1 adduct per 10(7) nucleotides, and the amount of tissue available for measurement is limited. Ion trap mass spectrometry has emerged as an important technique to screen for DNA adducts because of the high level sensitivity and selectivity, particularly when employing multi-stage scanning (MS(n) ). The product ion spectra provide rich structural information and corroborate the adduct identities even at trace levels in human tissues. Ion trap technology represents a significant advance in measuring DNA adducts in humans. © 2016 by John Wiley & Sons, Inc.
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http://dx.doi.org/10.1002/cpnc.12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5027840PMC
September 2016

Design of plasmonic photodetector with high absorptance and nano-scale active regions.

Opt Express 2016 Aug;24(16):18229-43

We propose a novel plasmonic photodetector with high responsivity, utilizing nano-scale active regions. This design can be applied to diverse materials (group III-V or IV materials) and different operation wavelengths covering the O-U bands. The periodic structure utilizing Surface Plasmon Polariton Bloch Waves (SPP-BWs) has low optical power loss. FDTD simulation shows an absorptance of 74.4% which means a responsivity of about 0.74 A/W at 1550 nm. The low capacitance brings low noise, reduced power consumption, and a high electrical bandwidth which is estimated to be 140 GHz. Among the plasmonic PDs with inherent high speeds but low responsivities, our design makes the obvious progress on improving the absorptance.
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http://dx.doi.org/10.1364/OE.24.018229DOI Listing
August 2016

Multiclass Carcinogenic DNA Adduct Quantification in Formalin-Fixed Paraffin-Embedded Tissues by Ultraperformance Liquid Chromatography-Tandem Mass Spectrometry.

Anal Chem 2016 05 15;88(9):4780-7. Epub 2016 Apr 15.

Masonic Cancer Center and ‡Department of Medicinal Chemistry, University of Minnesota , 2231 Sixth Street SE, Minneapolis, Minnesota 55455, United States.

DNA adducts are a measure of internal exposure to genotoxicants and an important biomarker for human risk assessment. However, the employment of DNA adducts as biomarkers in human studies is often restricted because fresh-frozen tissues are not available. In contrast, formalin-fixed paraffin-embedded (FFPE) tissues with clinical diagnosis are readily accessible. Recently, our laboratory reported that DNA adducts of aristolochic acid, a carcinogenic component of Aristolochia herbs used in traditional Chinese medicines worldwide, can be recovered quantitatively from FFPE tissues. In this study, we have evaluated the efficacy of our method for retrieval of DNA adducts from archived tissue by measuring DNA adducts derived from four other classes of human carcinogens: polycyclic aromatic hydrocarbons (PAHs), aromatic amines, heterocyclic aromatic amines (HAAs), and N-nitroso compounds (NOCs). Deoxyguanosine (dG) adducts of the PAH benzo[a]pyrene (B[a]P), 10-(deoxyguanosin-N(2)-yl)-7,8,9-trihydroxy-7,8,9,10-tetrahydrobenzo[a]pyrene (dG-N(2)-B[a]PDE); the aromatic amine 4-aminobiphenyl (4-ABP), N-(deoxyguanosin-8-yl)-4-aminobiphenyl (dG-C8-4-ABP); the HAA 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), N-(deoxyguanosin-8-yl)-PhIP (dG-C8-PhIP); and the dG adducts of the NOC 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), O(6)-methyl-dG (O(6)-Me-dG) and O(6)-pyridyloxobutyl-dG (O(6)-POB-dG), formed in liver, lung, bladder, pancreas, or colon were recovered in comparable yields from fresh-frozen and FFPE preserved tissues of rodents treated with the procarcinogens. Quantification was achieved by ultraperformance liquid chromatography coupled with electrospray ionization ion-trap multistage mass spectrometry (UPLC/ESI-IT-MS(3)). These advancements in the technology of DNA adduct retrieval from FFPE tissue clear the way for use of archived pathology samples in molecular epidemiology studies designed to assess the causal role of exposure to hazardous chemicals with cancer risk.
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http://dx.doi.org/10.1021/acs.analchem.6b00124DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4854775PMC
May 2016

Comparative DNA adduct formation and induction of colonic aberrant crypt foci in mice exposed to 2-amino-9H-pyrido[2,3-b]indole, 2-amino-3,4-dimethylimidazo[4,5-f]quinoline, and azoxymethane.

Environ Mol Mutagen 2016 Mar 6;57(2):125-36. Epub 2016 Jan 6.

Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota.

Considerable evidence suggests that environmental factors, including diet and cigarette smoke, are involved in the pathogenesis of colon cancer. Carcinogenic nitroso compounds (NOC), such as N-nitrosodimethylamine (NDMA), are present in tobacco and processed red meat, and NOC have been implicated in colon cancer. Azoxymethane (AOM), commonly used for experimental colon carcinogenesis, is an isomer of NDMA, and it produces the same DNA adducts as does NDMA. Heterocyclic aromatic amines (HAAs) formed during the combustion of tobacco and high-temperature cooking of meats are also associated with an elevated risk of colon cancer. The most abundant carcinogenic HAA formed in tobacco smoke is 2-amino-9H-pyrido[2,3-b]indole (AαC), whereas 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) is the most potent carcinogenic HAA formed during the cooking of meat and fish. However, the comparative tumor-initiating potential of AαC, MeIQ, and AOM is unknown. In this report, we evaluate the formation of DNA adducts as a measure of genotoxicity, and the induction of colonic aberrant crypt foci (ACF) and dysplastic ACF, as an early measure of carcinogenic potency of these compounds in the colon of male A/J mice. Both AαC and AOM induced a greater number of DNA adducts than MeIQ in the liver and colon. AOM induced a greater number of ACF and dysplastic ACF than either AαC or MeIQ. Conversely, based on adduct levels, MeIQ-DNA adducts were more potent than AαC- and AOM-DNA adducts at inducing ACF. Long-term feeding studies are required to relate levels of DNA adducts, induction of ACF, and colon cancer by these colon genotoxicants.
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http://dx.doi.org/10.1002/em.21993DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4752904PMC
March 2016

Method to Biomonitor the Cooked Meat Carcinogen 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in Dyed Hair by Ultra-Performance Liquid Chromatography-Orbitrap High Resolution Multistage Mass Spectrometry.

Anal Chem 2015 Jun 22;87(12):5872-7. Epub 2015 May 22.

†Masonic Cancer Center and Department of Medicinal Chemistry, College of Pharmacy, University of Minnesota, 2231 Sixth Street SE, Minneapolis, Minnesota 55455, United States.

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is a carcinogenic heterocyclic aromatic amine formed in cooked meat. The use of naturally colored hair containing PhIP can serve as a long-term biomarker of exposure to this carcinogen. However, the measurement of PhIP in dyed hair, a cosmetic treatment commonly used by the adult population, is challenging because the dye process introduces into the hair matrix a complex mixture of chemicals that interferes with the measurement of PhIP. The high-resolution scanning features of the Orbitrap Fusion mass spectrometer were employed to biomonitor PhIP in dyed hair. Because of the complexity of chemicals in the hair dye, the consecutive reaction monitoring of PhIP at the MS(3) scan stage was employed to selectively remove the isobaric interferences. The limit of quantification (LOQ) of PhIP was 84 parts-per-trillion (ppt) employing 50 mg of hair. Calibration curves were generated in dyed hair matrixes and showed good linearity (40-1000 pg PhIP/g hair) with a goodness-of-fit regression value of r(2) > 0.9978. The within-day (between-day) coefficients of variation were 7.7% (17%) and 5.4% (6.1%), respectively, with dyed hair samples spiked with PhIP at 200 and 600 ppt. The levels of PhIP accrued in dyed hair from volunteers on a semicontrolled feeding study who ingested known levels of PhIP were comparable to the levels of PhIP accrued in hair of subjects with natural hair color. The method was successfully employed to measure PhIP in nondyed and dyed hair biospecimens of participants in a case-control study of colorectal adenoma on their regular diet.
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http://dx.doi.org/10.1021/acs.analchem.5b01129DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4470769PMC
June 2015

Ultrastable silver nanoparticles.

Nature 2013 Sep 4;501(7467):399-402. Epub 2013 Sep 4.

Department of Chemistry, University of Toledo, Toledo, Ohio 43606, USA.

Noble-metal nanoparticles have had a substantial impact across a diverse range of fields, including catalysis, sensing, photochemistry, optoelectronics, energy conversion and medicine. Although silver has very desirable physical properties, good relative abundance and low cost, gold nanoparticles have been widely favoured owing to their proved stability and ease of use. Unlike gold, silver is notorious for its susceptibility to oxidation (tarnishing), which has limited the development of important silver-based nanomaterials. Despite two decades of synthetic efforts, silver nanoparticles that are inert or have long-term stability remain unrealized. Here we report a simple synthetic protocol for producing ultrastable silver nanoparticles, yielding a single-sized molecular product in very large quantities with quantitative yield and without the need for size sorting. The stability, purity and yield are substantially better than those for other metal nanoparticles, including gold, owing to an effective stabilization mechanism. The particular size and stoichiometry of the product were found to be insensitive to variations in synthesis parameters. The chemical stability and structural, electronic and optical properties can be understood using first-principles electronic structure theory based on an experimental single-crystal X-ray structure. Although several structures have been determined for protected gold nanoclusters, none has been reported so far for silver nanoparticles. The total structure of a thiolate-protected silver nanocluster reported here uncovers the unique structure of the silver thiolate protecting layer, consisting of Ag2S5 capping structures. The outstanding stability of the nanoparticle is attributed to a closed-shell 18-electron configuration with a large energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, an ultrastable 32-silver-atom excavated-dodecahedral core consisting of a hollow 12-silver-atom icosahedron encapsulated by a 20-silver-atom dodecahedron, and the choice of protective coordinating ligands. The straightforward synthesis of large quantities of pure molecular product promises to make this class of materials widely available for further research and technology development.
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http://dx.doi.org/10.1038/nature12523DOI Listing
September 2013

Temporal stability of magic-number metal clusters: beyond the shell closing model.

Nanoscale 2013 Mar 1;5(5):2036-44. Epub 2013 Feb 1.

Department of Chemistry, The University of Toledo, Toledo, OH 43606, USA.

The anomalous stability of magic-number metal clusters has been associated with closed geometric and electronic shells and the opening of HOMO-LUMO gaps. Despite this enhanced stability, magic-number clusters are known to decay and react in the condensed phase to form other products. Improving our understanding of their decay mechanisms and developing strategies to control or eliminate cluster instability is a priority, to develop a more complete theory of their stability, to avoid studying mixtures of clusters produced by the decay of purified materials, and to enable technology development. Silver clusters are sufficiently reactive to facilitate the study of the ambient temporal stability of magic-number metal clusters and to begin to understand their decay mechanisms. Here, the solution phase stability of a series of silver:glutathione (Ag:SG) clusters was studied as a function of size, pH and chemical environment. Cluster stability was found to be a non-monotonic function of size. Electrophoretic separations showed that the dominant mechanism involved the redistribution of mass toward smaller sizes, where the products were almost exclusively previously known cluster sizes. Optical absorption spectra showed that the smaller clusters evolved toward the two most stable cluster sizes. The net surface charge was found to play an important role in cluster stabilization although charge screening had no effect on stability, contrary to DLVO theory. The decay mechanism was found to involve the loss of Ag(+) ions and silver glutathionates. Clusters could be stabilized by the addition of Ag(+) ions and destabilized by either the addition of glutathione or the removal of Ag(+) ions. Clusters were also found to be most stable in near neutral pH, where they had a net negative surface charge. These results provide new mechanistic insights into the control of post-synthesis stability and chemical decay of magic-number metal clusters, which could be used to develop design principles for synthesizing specific cluster species.
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http://dx.doi.org/10.1039/c3nr33705gDOI Listing
March 2013

Mass spectrometric identification of silver nanoparticles: the case of Ag32(SG)19.

Anal Chem 2012 Jun 4;84(12):5304-8. Epub 2012 Jun 4.

Department of Chemistry, University of Toledo, Toledo, Ohio 43606, USA.

Mass spectrometry has played a key role in identifying the members of a series of gold clusters, which has enabled the development of magic-number cluster theory. The successes of the gold cluster system have yet to be repeated in another metal cluster system, however. Silver clusters in particular have proven to be challenging due to their relative instability compared with gold clusters. Using the well-characterized gold nanocluster, Au(25)(SG)(18), we present optimized electrospray ionization mass spectrometry (ESI-MS) instrumental parameters for the maximal transmission of the intact cluster. Parameters shown to have the largest effect on intact cluster transmission/detection include trap and transfer collision energy, source temperature, and cone gas flow rate. Herein we describe a general strategy to acquire mass spectra of fragile metal clusters with reliable mass assignments. By also optimizing sample solution conditions, high-quality ESI mass spectra of a prototypical silver:glutathione (Ag:SG) cluster were obtained without significant fragmentation. By using gentle conditions and solution conditions designed to stabilize the clusters, fragmentation was dramatically reduced and mass spectra with isotopic resolution were measured. Using this strategy, we have made the first formula assignment for a ligand-protected Ag cluster of Ag(32)(SG)(19).
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http://dx.doi.org/10.1021/ac300536jDOI Listing
June 2012

Allosteric interaction of nucleotides and tRNA(ala) with E. coli alanyl-tRNA synthetase.

Biochemistry 2011 Nov 19;50(45):9886-900. Epub 2011 Oct 19.

Department of Biochemistry and Cancer Biology, University of Toledo College of Medicine, Toledo, Ohio 43614, United States.

Alanyl-tRNA synthetase, a dimeric class 2 aminoacyl-tRNA synthetase, activates glycine and serine at significant rates. An editing activity hydrolyzes Gly-tRNA(ala) and Ser-tRNA(ala) to ensure fidelity of aminoacylation. Analytical ultracentrifugation demonstrates that the enzyme is predominately a dimer in solution. ATP binding to full length enzyme (ARS875) and to an N-terminal construct (ARS461) is endothermic (ΔH = 3-4 kcal mol(-1)) with stoichiometries of 1:1 for ARS461 and 2:1 for full-length dimer. Binding of aminoacyl-adenylate analogues, 5'-O-[N-(L-alanyl)sulfamoyl]adenosine (ASAd) and 5'-O-[N-(L-glycinyl)sulfamoyl]adenosine (GSAd), are exothermic; ASAd exhibits a large negative heat capacity change (ΔC(p) = 0.48 kcal mol(-1) K(-1)). Modification of alanyl-tRNA synthetase with periodate-oxidized tRNA(ala) (otRNA(ala)) generates multiple, covalent, enzyme-tRNA(ala) products. The distribution of these products is altered by ATP, ATP and alanine, and aminoacyl-adenylate analogues (ASAd and GSAd). Alanyl-tRNA synthetase was modified with otRNA(ala), and tRNA-peptides from tryptic digests were purified by ion exchange chromatography. Six peptides linked through a cyclic dehydromoropholino structure at the 3'-end of tRNA(ala) were sequenced by mass spectrometry. One site lies in the N-terminal adenylate synthesis domain (residue 74), two lie in the opening to the editing site (residues 526 and 585), and three (residues 637, 639, and 648) lie on the back side of the editing domain. At least one additional modification site was inferred from analysis of modification of ARS461. The location of the sites modified by otRNA(ala) suggests that there are multiple modes of interaction of tRNA(ala) with the enzyme, whose distribution is influenced by occupation of the ATP binding site.
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http://dx.doi.org/10.1021/bi2012004DOI Listing
November 2011

Hemoglobin redux: combining neutron and X-ray diffraction with mass spectrometry to analyse the quaternary state of oxidized hemoglobins.

Acta Crystallogr D Biol Crystallogr 2010 Nov 20;66(Pt 11):1249-56. Epub 2010 Oct 20.

Department of Chemistry, University of Toledo, Toledo, OH 43606, USA.

Improvements in neutron diffraction instrumentation are affording the opportunity to re-examine the structures of vertebrate hemoglobins and to interrogate proton and solvent position changes between the different quaternary states of the protein. For hemoglobins of unknown primary sequence, structural studies of cyanomethemoglobin (CNmetHb) are being used to help to resolve sequence ambiguity in the mass spectra. These studies have also provided additional structural evidence for the involvement of oxidized hemoglobin in the process of erythrocyte senescence. X-ray crystal studies of Tibetan snow leopard CNmetHb have shown that this protein crystallizes in the B state, a structure with a more open dyad, which possibly has relevance to RBC band 3 protein binding and erythrocyte senescence. R-state equine CNmetHb crystal studies elaborate the solvent differences in the switch and hinge region compared with a human deoxyhemoglobin T-state neutron structure. Lastly, comparison of histidine protonation between the T and R state should enumerate the Bohr-effect protons.
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http://dx.doi.org/10.1107/S090744491002545XDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2967423PMC
November 2010