MALDI-TOF Spectrum Research Articles

Feature selection in GC-MS, NMR and MALDI-TOF spectra of tar sand bitumen

Expectations from unconventional reservoirs are often overly optimistic when estimation criteria are transferred from one location to another but some of the many important elements of petroleum systems remain unaccounted for. Feature engineering used in model construction to improve the quality of the machine learning process can improve the performance of unconventional reservoir estimates.The compositions of petroleum fluids are represented by spectra obtained from various analyses, which vary greatly in shape and dimensions, contain large amounts of data, and cannot be processed as single numbers. Selection of relevant features in the spectra can simplify interpretation, reduce dimensionality, and improve data compatibility.The features have been selected in GC-MS, NMR and MALDI-TOF spectra of bitumen from the Bayan-Erkhet tar sand deposit in Mongolia for comparison with bitumens from other regions of the world. The GC-MS spectra have a similar baseline shape, either a triangle or two humps with peaks eluted to varying degrees. The comparison made it possible to isolate poorly eluted peaks of carbon number groups in the studied bitumen. Since NMR spectra of petroleum fluids are most often published without NMR parameters, simple indices are developed to compare the shapes of the spectra. The values of these indices are consistent with the characteristics of the samples. The sequences of hydrocarbon compounds determined in the MALDI-TOF spectrum are very similar to those of the Banik black shale, Iraq, which allowed to clarify the sequences. Some peaks are also found in the spectra of two other crude oil samples. The feature selection in spectral analyses enables revealing the hidden information.

Photoinduced Strain-Assisted Synthesis of a Stiff-Stilbene Polymer by Ring-Opening Metathesis Polymerization.

Developing a novel strategy to synthesize photoresponsive polymers is of significance owing to their potential applications. We report a photoinduced strain‐assisted synthesis of main‐chain stiff‐stilbene polymers by using ring‐opening metathesis polymerization (ROMP), activating a macrocyclic π‐bond connected to a stiff‐stilbene photoswitch through a linker. Since the linker acts as an external constraint, the photoisomerization to the E‐form leads to the stiff‐stilbene being strained and thus reactive to ROMP. The photoisomerization of Z‐form to E‐form was investigated using time‐dependent NMR studies and UV/Vis spectroscopy. The DFT calculation showed that the E‐form was less stable due to a lack of planarity. By the internal strain developed due to the linker constraint through photoisomerization, the E‐form underwent ROMP by a second generation Grubbs catalyst. In contrast, Z‐form did not undergo polymerization under similar conditions. The MALDI‐TOF spectrum of E‐form after polymerization showed the presence of oligomers of >5.2 kDa.

Kinetic and biocompatibility investigation on the catalytic ring opening polymerization of l-lactide in bulk using cyclic Bu2Sn initiators derived from ethylene glycol, pentaerythritol and cloisite 30B

In the present work, considering a green approach, PLLA was synthesized by the ring-opening polymerization of l-LA using various cyclic initiators (2,2-dibutyl-2-stanna-1,3-dioxacyclo ethane (1), spirocyclic tin (3) and cloisite modified tin (5)). PLLA was characterized by size exclusion chromatography, differential scanning calorimetry, 1H and 13C NMR, XRD and MALDI-TOF. The molecular weight distribution was narrow (<1.5) for both low and high molecular weights (>85,000 g/mol). An X-ray study showed the crystalline nature of PLLA, irrespective of the different types of initiators and polymerization conditions. A kinetic investigation showed that all polymerizations were first order with respect to the monomer and no termination reactions occurred during the polymerization. MALDI-TOF spectra of PLLA chains doped with Na+ and K+ cations show that the PLLA prepared using initiators 1 and 3 have hydroxyl and carboxyl end groups without incorporation of tin. The MALDI-TOF spectrum of PLLA prepared using initiator 5 also enabled the simultaneous detection of the linear and cyclic structure of PLLA without tin. Biocompatible and biodegradable PLLA was obtained, which could be used for biomedical applications.

Empirical study of petroleum-based pitch production via pressure- and temperature-controlled thermal reactions

Three-stage thermal reactions were conducted to investigate empirical trends of petroleum-based pitch production and the chemical characteristics of pitch produced by controlling the temperature and pressure operating parameters. The softening point of pitch increased with increasing reaction temperature under atmospheric pressure, whereas the pitch yield increased with decreasing reaction temperature under a pressurized condition. Elemental analysis supported the result of decreased hydrogen content. In addition, thermogravimetric analysis revealed that higher reaction temperatures could induce the polymerization and condensation of polyaromatic hydrocarbons (PAHs) with carbon yield at 900°C. The molecular weight distribution (MWD) of pitch was analyzed by MALDI-TOF analysis according to the operating parameters during the thermal reaction. The MALDI-TOF spectrum was normalized to observe the variation in the MWD by Anthracene (178Da) as a pseudo-component. Range 2–3 and range 6–8 in the MWD coincided with the trends of the pitch yield and the softening point, respectively. The results suggested that pitch yield is related to the PAHs with 2–6 aromatic rings and that the softening point is related to highly condensed PAHs with more than 6 aromatic rings. The anisotropy/isotropy of the pitch was analyzed by polarized light microscopy. The pitch produced under the pressurized condition was isotropic. However, the pitch produced under atmospheric pressure exhibited a well-oriented domain texture. We concluded that volatile contents disturb the polymerization and condensation of PAHs because of side reactions involving the aliphatic contents.

Validation of a New Web Application for Identification of Fungi by Use of Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry.

Matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) mass spectrometry has emerged as a reliable technique to identify molds involved in human diseases, including dermatophytes, provided that exhaustive reference databases are available. This study assessed an online identification application based on original algorithms and an extensive in-house reference database comprising 11,851 spectra (938 fungal species and 246 fungal genera). Validation criteria were established using an initial panel of 422 molds, including dermatophytes, previously identified via DNA sequencing (126 species). The application was further assessed using a separate panel of 501 cultured clinical isolates (88 mold taxa including dermatophytes) derived from five hospital laboratories. A total of 438 (87.35%) isolates were correctly identified at the species level, while 26 (5.22%) were assigned to the correct genus but the wrong species and 37 (7.43%) were not identified, since the defined threshold of 20 was not reached. The use of the Bruker Daltonics database included in the MALDI Biotyper software resulted in a much higher rate of unidentified isolates (39.76 and 74.30% using the score thresholds 1.7 and 2.0, respectively). Moreover, the identification delay of the online application remained compatible with real-time online queries (0.15 s per spectrum), and the application was faster than identifications using the MALDI Biotyper software. This is the first study to assess an online identification system based on MALDI-TOF spectrum analysis. We have successfully applied this approach to identify molds, including dermatophytes, for which diversity is insufficiently represented in commercial databases. This free-access application is available to medical mycologists to improve fungal identification.

SYNTHESIS AND STRUCTURE OF 4-(9-HYDROXY-1,4,7-TRIOXYNONYL)PHTHALONITRILE

4-(9-Hydroxy-1,4,7-trioxynonyl)phthalonitrile was prepared by reaction of 4-nitrophthalonitrile with triethylene glycol in dry DMSO in the presence of fresh-calcined fine milled K2CO3 at 60 °C for 12 hours. The reaction mixture was poured into cold distilled water and extracted by CH2Cl2. Then the crude product obtained after solvent evaporation was purified by column chromatography on silica gel using elution mixture of ethyl acetate : hexane (1:3) and after that end product was dried at reduced pressure at 80 oC for 4 h. The product was characterized by IR and 1Н NMR spectroscopies, mass-spectrometry, elemental analysis and X-ray diffraction data. In MALDI-TOF spectrum, two signals located at 299 [M+Na]+ and 315 [M+К]+ Da were detected. Conformity between the calculated isotopic distributions and those derived from experimental data proves these assignments. A colorless monocrystal suitable for X-Ray measurements was grown up by low temperature solvent evaporation from a solution of 4-(9-hydroxy-1,4,7-trioxynonyl)phthalonitrile in ethyl acetate. X-ray studying showed that this compound is a monohydrate of 4-(9-hydroxy-1,4,7-trioxynonil)phthalonitrile with a water molecule located in lateral chain. Four molecules of 4-(9-hydroxy-1,4,7-trioxynonil)phthalonitrile and four water molecules were founded to be located in one unit cell with formatting eight intermolecular hydrogen bonds. Hence triethylene glycol fragment forms a chelate-like cavity which is able to hold a water molecule or a cation of alkali metal. It was found that its structure is very similar to that optimized at DFT/B3LYP/6-31G(d,p) level. The some bond lengths of theoretical calculations are found to be greater than experiment data because of close intermolecular interactions in solid state.Forcitation:Kuznetsova A.S., Dmitriev M.V., Zav’yalov A.V., Koifman O.I., Islyaikin M.K. Synthesis and structure of 4-(9-hydroxy-1,4,7-trioxynonyl)phthalonitrile. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 3. P. 15-21.

Crystal-to-Crystal Synthesis of Triazole-Linked Pseudo-proteins via Topochemical Azide-Alkyne Cycloaddition Reaction.

Isosteric replacement of amide bond(s) of peptides with surrogate groups is an important strategy for the synthesis of peptidomimetics (pseudo-peptides). Triazole is a well-recognized bio-isostere for peptide bonds, and peptides with one or more triazole units are of great interest for different applications. We have used a catalyst-free and solvent-free method, viz., topochemical azide-alkyne cycloaddition (TAAC) reaction, to synthesize pseudo-proteins with repeating sequences. A designed β-sheet-forming l-Ala-l-Val dipeptide containing azide and alkyne at its termini (N3-Ala-Val-NHCH2C≡CH, 1) was synthesized. Single-crystal XRD analysis of the dipeptide 1 showed parallel β-sheet arrangement along the b-direction and head-to-tail arrangement of such β-sheets along the c-direction. This head-to-tail arrangement along the c-direction places the complementary reacting motifs, viz., azide and alkyne, of adjacent molecules in proximity. The crystals of dipeptide 1, upon heating at 85 °C, underwent crystal-to-crystal polymerization, giving 1,4-triazole-linked pseudo-proteins. This TAAC polymerization was investigated by various time-dependent techniques, such as NMR, IR, DSC, and PXRD. The crystal-to-crystal nature of this transformation was revealed from polarizing microscopy and PXRD experiments, and the regiospecificity of triazole formation was evidenced from various NMR techniques. The MALDI-TOF spectrum showed the presence of pseudo-proteins >7 kDa.

Allelic variation of LMW-GS composition in Chinese wheat landraces of the Yangtze-River region detected by MALDI-TOF-MS.

Low molecular weight glutenin subunits are important components of wheat storage proteins, which play an important role in determining end-use quality of common wheat. A newly established matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) procedure was used to analyze 478 landraces of bread wheat collected from the Yangtze-River region in China. Results indicated that 17 alleles at three loci: Glu-A3, Glu-B3 and Glu-D3 were identified, resulting in 87 different allele combinations. Of the 17 alleles detected at all the Glu-3 loci, five belonged to Glu-A3, seven to Glu-B3 and five to Glu-D3 locus. MALDI-TOF-MS indicated Glu-A3a/c was present in 72.8%, Glu-A3b in 8.4%, Glu-A3d in 8.4%, Glu-A3f in 5.2% and Glu-A3e in 3.6% lines. Seven types of alleles were identified at the Glu-B3 locus: Glu-B3d/i (25.5%), Glu-B3b (21.3%), Glu-B3c (16.9%), Glu-B3h (13.8%), Glu-B3f (8.4%), Glu-B3a (8.2%), and Glu-B3g (5.2%). Five types of Glu-D3 alleles were detected: Glu-D3a (58.4%), Glu-D3c (22.6%), Glu-D3d (15.5%), Glu-D3b (3.3%) and Glu-D3f (0.2%). Four new alleles that showed abnormal MALDI-TOF spectrum patterns were identified at the Glu-A3 and Glu-B3 loci. A detailed study is needed to further characterize these alleles and their potential usage for wheat improvement.

Genome sequence of Oceanobacillus picturae strain S1, an halophilic bacterium first isolated in human gut.

Oceanobacillus picturae is a strain of a moderately halophilic bacterium, first isolated from a mural painting. We demonstrate, for the first time, the culture of human Oceanobacillus picturae, strain S1T, whose genome is described here, from a stool sample collected from a 25-year-old Saoudian healthy individual. We used a slightly modified standard culture medium adding 100 g/L of NaCl. We provide a short description of this strain including its MALDI-TOF spectrum, the main identification tool currently used in clinical microbiology. The 3,675,175 bp long genome exhibits a G + C content of 39.15 % and contains 3666 protein-coding and 157 RNA genes. The draft genome sequence of Oceanobacillus picturae has a similar size to the Oceanobacillus kimchii (respectively 3.67 Mb versus 3.83 Mb). The G + C content was higher compared with Oceanobacillus kimchii (respectively 39.15 % and 35.2 %). Oceanobacillus picturae shared almost identical number of genes (3823 genes versus 3879 genes), with a similar ratio of genes per Mb (1041 genes/Mb versus 1012 genes/Mb).The genome sequencing of Oceanobacillus picturae strain S1 isolated for the first time in a human, will be added to the 778 genome projects from the gastrointestinal tract listed by the international consortium Human Microbiome Project.Electronic supplementary materialThe online version of this article (doi:10.1186/s40793-015-0081-2) contains supplementary material, which is available to authorized users.

Borrelia burgdorferi HtrA: evidence for twofold proteolysis of outer membrane protein p66.

In prokaryotes, members of the High Temperature Requirement A (HtrA) family of serine proteases function in the periplasm to degrade damaged or improperly folded membrane proteins. Borrelia burgdorferi, the agent of Lyme disease, codes for a single HtrA homolog. Two-dimensional electrophoresis analysis of B. burgdorferi B31A3 and a strain that overexpresses HtrA (A3HtrAOE) identified a downregulated protein in A3HtrAOE with a mass, pI and MALDI-TOF spectrum consistent with outer membrane protein p66. P66 and HtrA from cellular lysates partitioned into detergent-resistant membranes, which contain cholesterol-glycolipid-rich membrane regions known as lipid rafts, suggesting that HtrA and p66 may reside together in lipid rafts also. This agrees with previous work from our laboratory, which showed that HtrA and p66 are constituents of B. burgdorferi outer membrane vesicles. HtrA degraded p66 in vitro and A3HtrAOE expressed reduced levels of p66 in vivo. Fluorescence confocal microscopy revealed that HtrA and p66 colocalize in the membrane. The association of HtrA and p66 establishes that they could interact efficiently and their protease/substrate relationship provides functional relevance to this interaction. A3HtrAOE also showed reduced levels of p66 transcript in comparison with wild-type B31A3, indicating that HtrA-mediated regulation of p66 may occur at multiple levels.

Clostridium polynesiense sp. nov., a new member of the human gut microbiota in French Polynesia

Strain MS1, a Gram-positive, obligately anaerobic, motile and spore-forming rod belonging to the Clostridium genus, was isolated from the feces of a healthy Polynesian male living in French Polynesia. The temperature range for growth was 30–45 °C. We sequenced its complete genome and studied its phenotypic characteristics. The 3,560,738-bp long genome (one chromosome, no plasmid, G + C content 34%) contained 3535 protein-coding and 70 RNA genes. Strain MS1 exhibited a 98.24% 16S rRNA similarity with Clostridium amylolyticum, the phylogenetically closest species. When compared with other Clostridium species with standing in nomenclature, it had an average genomic similarity of 68.8–70%, a unique MALDI-TOF spectrum, and differed in nitrate reduction, motility and l-arabinose and d-lactose metabolism with most of the closest species. Therefore, strain MS1 is sufficiently distinct from type strains of the genus Clostridium to represent a novel species within this genus, for which the name Clostridium polynesiense sp. nov. is proposed. The type strain of C. polynesiense is MS1T (= CSUR P630 = DSM 27072).

Detection of carbapenemase-producing Enterobacteriaceae in various scenarios and health settings

Detection of carbapenemase-producing Enterobacteriaceae (CPE) is an important task at microbiology laboratories in hospitals. As the prevalence of CPE is increasing worldwide, the implementation of phenotypically based screening as well as confirmatory procedures to detect CPE are important for microbiologists. In addition to detection of carbapenem hydrolysis, the inhibition of activity against a carbapenem in the presence of several inhibitor compounds specific to class A, B, or class C beta-lactamases is a useful method to confirm the presence of carbapenemases in bacterial isolates. There is also a proteomic approach that compares the MALDI-TOF spectrum generated by the intact carbapenem (non-hydrolyzed) with that obtained after hydrolysis of the beta-lactam ring by beta-lactamase to reveal the presence of carbapenemases in bacterial isolates. Proteomic methods will probably be more frequently implemented in laboratories in the near future. Finally, molecular methods to directly or indirectly detect the presence of a carbapenemase genes are increasingly being used in microbiology laboratories. One of the main advantages of these methods is their speed, and also that they can be used directly with the clinical sample without the need for an isolated bacterial colony. Multiplex PCR, real-time PCR, DNA microarrays and pyrosequencing are some examples of molecular-based tests. Their main disadvantage is their cost, although prices are going down as the range of services increases. Surveillance of carriers is also an important task for infection control purposes. In this case, commercially available chromogenic medium supplemented with low carbapenem concentrations has shown an excellent ability to detect CPE. Moreover, molecular methods to detect specific carbapenemase genes directly from rectal swabs, stools, or other colonization sources have had excellent results.

Synthesis and caracterization of macromonomers of poly (2-methyl-2-oxazoline)-allyl by an acid exchanged clay as eco-catalyst

Macromonomers from oxazoline derivates were synthesized by using in conjunction with ethylenically unsaturated modifier. allyl chloride (AC) is chosen as representative modifier for the synthesis of allyl-terminated macromonomers in the presence of an acid exchanged montmorillonite as catalyst. The macromonomers were characterized by FT-IR, 1H-NMR, 13C-NMR and MALDI-TOF mass spectroscopy. The effects of amount of catalyst, amount of initiator, solvent and temperature on yields and intrinsic viscosity were studied. NMR and IR spectra of macromonomers show characteristic chemical shifts absorptions of the ethylenically unsaturated group of the modifier. The MALDI-TOF spectrum shows that the macromonomers synthesized accordingly are terminated with ethylenically unsaturated group of modifier at one end of the polymer chain and a hydroxyl group at the other end.

Separation and characterization of dextran extracted from deteriorated sugarcane

In this research work, dextran was extracted from deteriorated sugarcane by alcohol precipitation and purified by gel filtration chromatography. Total acid hydrolysis and enzymatic degradation were utilized to confirm the purity of separated polysaccharide. Using the more recently available techniques such as (1H,13C) and two-dimensional (COSY and HMQC) NMR spectral analysis, methylation GC–MS and MALDI-TOF mass spectrometry, the structure of sugarcane dextran (SC-Dex) was investigated. On the basis of all spectra, SC-Dex showed a branched polysaccharide that contained only d-glucose residues in consecutive α-(1–6) linkages in the main chain with α-(1–3) branches. Methylation analysis showed that, the degree of α-(1–3) branching levels was 4.37%. Several structural fragments were identified from MALDI-TOF spectrum with peak-to-peak mass difference of 162gmol−1, which confirmed that the repeat unit in SC-Dex was d-glucose. The surface morphology of SC-Dex, revealed the spherically shaped and porous structure. Using HPSEC–MALLS–RI system, the average molecular weight of SC-Dex was estimated to be 1.753×106gmol−1 with an index of polydispersity value of 1.069.

In vivo examination of 111In-bis-5HT-DTPA to target myeloperoxidase in atherosclerotic ApoE knockout mice

Purpose: The aim of the study is to assess the feasibility of imaging specific activity of myeloperoxidase (MPO), a leukocyte-derived enzyme with important role in atherosclerosis, by SPECT/CT using a novel radiotracer, 111In-bis-5-hydroxytryptamide-diethylenetriamine-pentaacetate (111In-bis-5HT-DTPA).Methods: Bis-5HT-DTPA was synthesized. Oligomerization of bis-5HT-DTPA in the presence of MPO/H2O2 was studied and confirmed using MALDI-TOF. Apolipoprotein E knockout (ApoE KO) mice was used as an atherosclerosis-prone rodent model. Biodistribution assay and micro SPECT/CT imaging were carried out to prove the atherosclerosis targeting of 111In-bis-5HT-DTPA in the ApoE KO mice.Results: MALDI-TOF spectrum showed that the 5HT base agent can self oligomerize after activating by MPO. From the biodistribution study, 111In-bis-5HT-DTPA was quantified to be retained markedly higher while eliminated much slower in the aortas of the ApoE KO mice than that of the wild type (WT) mice within 1 h post-injection. The nuclear imaging showed significantly higher uptake in the aorta of the ApoE KO mice than that of the WT mice at least within 2 h post-injection.Conclusion: This study described the pharmacokinetics and biodistribution of 111In-bis-5HT-DTPA in ApoE KO mice and validated its utilization for early detection of atherosclerotic marker, MPO, in the aortic wall of atherosclerosis-prone rodent model.

Structural investigation of a glycoprotein from gum ghatti

The glycoprotein structure of gum ghatti was investigated. The covalent bonding between polysaccharides and proteins was firstly confirmed by high performance size exclusion chromatography (HPSEC) using refractive index (RI) and UV detectors. Partial acid hydrolysis and enzymatic degradation were also utilized. Several structural fragments such as AraHex2-HexA-HexNAc, Hex4HexNAc2, AraHex4HexNAc, Hex10HexNAc and Hex4HexNAc-Asn were identified from MALDI-TOF spectrum; using 1D and 2D NMR spectra, the linkage site of amino acids and polysaccharides was determined as N-linked (Hex)n-GlcNAc-Asn. Combined with the polysaccharide structure obtained before, a glycoprotein structure model was proposed. It was composed of 1,6-linked galactose backbone, which were attached by numerous of sugar side chains and peptide chains.

Purification and Characterization of Polyphenols from Chestnut Astringent Skin

Polyphenolic compounds from chestnut astringent skin (CAS) were purified by dialysis, using Diaion HP-20 and Sephadex LH-20 columns. During purification, specific α-amylase inhibitory activities were increased about 3.4-fold, and the 50% inhibition value was 5.71 μg/mL in the Sephadex LH-20 fraction (SE-fraction). The SE-fraction contained about 67% of the total polyphenols, 57.3% of the flavanol-type tannins, and 51.3% of the procyanidins. Strong antioxidant activity was observed in the SE-fraction. Oral administration of the SE-fraction in rats fed corn starch significantly suppressed an increase in blood glucose levels. The SE-fraction contained gallic acid and ellagic acid. The MALDI-TOF spectrum showed a peak series exhibiting a mass increment of 288 Da, reflecting the variation in the number of catechin/epicatechin units. Our results suggest CAS contains polyphenols with strong α-amylase inhibitory activity. The data also suggest CAS polyphenols might be oligomeric proanthocyanidins with gallic acid and ellagic acid.

Human T-lymphotropic Virus Type 1 p30 Interacts with REGγ and Modulates ATM (Ataxia Telangiectasia Mutated) to Promote Cell Survival

Human T-lymphotropic virus type 1 (HTLV-1) is a causative agent of adult T cell leukemia/lymphoma and a variety of inflammatory disorders. HTLV-1 encodes a nuclear localizing protein, p30, that selectively alters viral and cellular gene expression, activates G(2)-M cell cycle checkpoints, and is essential for viral spread. Here, we used immunoprecipitation and affinity pulldown of ectopically expressed p30 coupled with mass spectrometry to identify cellular binding partners of p30. Our data indicate that p30 specifically binds to cellular ATM (ataxia telangiectasia mutated) and REGγ (a nuclear 20 S proteasome activator). Under conditions of genotoxic stress, p30 expression was associated with reduced levels of ATM and increased cell survival. Knockdown or overexpression of REGγ paralleled p30 expression, suggesting an unexpected enhancement of p30 expression in the presence of REGγ. Finally, size exclusion chromatography revealed the presence of p30 in a high molecular mass complex along with ATM and REGγ. On the basis of our findings, we propose that HTLV-1 p30 interacts with ATM and REGγ to increase viral spread by facilitating cell survival.

CHESTNUT BURS AS A SOURCE OF NATURAL ANTIOXIDANTS

The potential of chestnut bur as a source of natural antioxidants has been studied. Extracts in solvents of varying polarity (acetone, ethanol, methanol and water) were obtained and compared with respect to extraction yield, total phenols content, antioxidant activity, molecular weight distribution and composition. The extraction with water led to the highest extraction yield (21.2%) and extract total phenols content (37.6 g GAE/100g), FRAP antioxidant activity (2120 nmol AAE/mg extract), DPPH and ABTS radical scavenging activity (3.68 and 3.59 mmol TRE/g extract, respectively) together with the lowest EC50 values for the DPPH (0.044 mg/mL) and ABTS (0.337 mg/mL) essays. The extraction yield, the extract total phenols content and the antioxidant activity (FRAP, DPPH and ABTS) decreased when the polarity of the solvent decreased (water >methanol>ethanol>acetone) and the EC50 values increased in the same order. Chestnut bur extracts have been characterized as hydrolysable gallotannins as revealed its MALDI-TOF spectrum showing a major peak series exhibiting a mass increment of 152 Da corresponding to the repeat unit of the galloyl group. In addition to gallic acid esters of glucose, ellagic acid, quercetin, quercetin-3βD-glucoside and vescalagin/castalagin were found in chestnut bur extracts.

Determination of protein synthesis in vivo using labeling from deuterated water and analysis of MALDI-TOF spectrum

This paper describes a method of determining protein synthesis and turnover using in vivo labeling of protein with deuterated water and analysis of matrix-assisted laser desorption time-of-flight mass spectrometer (MALDI-TOF) spectrum. Protein synthesis is calculated using mass isotopomer distribution analysis instead of precursor to product amino acid enrichment ratio. During protein synthesis, the incorporation of deuterium from water changes the mass isotopomer distribution (isotope envelop) according to the number of deuterium atoms (0, 1, 2, 3, etc.) incorporated, and the distribution of the protein with 0, 1, 2, 3,... atoms of deuterium follows a binomial distribution. A mathematical algorithm by which the distribution of deuterium isotopomers can be extracted from the observed MALDI-TOF spectrum is presented. Since deuterium isotopomers are unique to newly synthesized proteins, the quantitation of their distribution provides a method for the quantitation of newly synthesized proteins. The combined use of postsource decay sequence identification and mass isotopomer distribution analysis makes the use of in vivo labeling with deuterated water a precise method to determine specific protein synthesis.