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At least 865 records · Page 48Linked to original sources
PubMed2005

Metabolomics in the context of systems biology: bridging traditional Chinese medicine and molecular pharmacology.

The introduction of the concept of systems biology, enabling the study of living systems from a holistic perspective based on the profiling of a multitude of biochemical components, opens up a unique and novel opportunity to reinvestigate natural products. In the study of their bioactivity, the necessary reductionistic approach on single active components has been successful in the discovery of new medicines, but at the same time the synergetic effects of components were lost. Systems biology, and especially metabolomics, is the ultimate phenotyping. It opens up the possibility of studying the effect of complex mixtures, such as those used in Traditional Chinese Medicine, in complex biological systems; abridging it with molecular pharmacology. This approach is considered to have the potential to revolutionize natural product research and to advance the development of scientific based herbal medicine.

Drugs, Chinese Herbal↗
PubMed1983

Relative singularity/mixedness judgements for selected taste stimuli.

Quinine hydrochloride, fructose, citric acid, NaCl, monosodium glutamate, KCl, and mixtures of two, three and four solutes were rated and ranked along a continuum from "single" to "mixed" tasting. Quinine was judged most singular, with fructose and citric acid forming a second most singular group. Other stimuli were intermediate while the mixtures were judged most mixed, the mixedness increasing with mixture complexity. When NaCl and fructose were judged with their binary mixtures in the same manner, the degree of mixedness of the mixtures varied with the proportions of the components.

Adolescent↗
PubMed2004

HPLC-MSn analysis of phenolic compounds and purine alkaloids in green and black tea.

Tea is a complex mixture containing a range of compounds from simple phenolics to complex thearubigins, many of which have well-recognized antioxidant properties. This paper describes the application of high-performance liquid chromatography-mass spectrometry (HPLC-MS(n)) methods for the rapid and routine analysis of more than 30 phenolics in tea. Green and black tea infusions were injected directly onto a reversed phase HPLC column, and the phenolics eluted using two different mobile phase gradients, one optimized to resolve catechin derivatives and the other, flavonols and theaflavins. Compounds, identified on the basis of their retention time, absorbance spectrum, and MS fragmentation pattern, included (+)-catechin, (-)-epicatechin, theaflavin and their various gallate derivatives, quercetin and kaempferol mono-, di-, and triglycosides, quinic acid esters of gallic acid and hydroxycinnamates, and the purine alkaloids, caffeine and theobromine.

Biflavonoids↗
PubMed2003

Synergistic computational and experimental proteomics approaches for more accurate detection of active serine hydrolases in yeast.

An analysis of the structurally and catalytically diverse serine hydrolase protein family in the Saccharomyces cerevisiae proteome was undertaken using two independent but complementary, large-scale approaches. The first approach is based on computational analysis of serine hydrolase active site structures; the second utilizes the chemical reactivity of the serine hydrolase active site in complex mixtures. These proteomics approaches share the ability to fractionate the complex proteome into functional subsets. Each method identified a significant number of sequences, but 15 proteins were identified by both methods. Eight of these were unannotated in the Saccharomyces Genome Database at the time of this study and are thus novel serine hydrolase identifications. Three of the previously uncharacterized proteins are members of a eukaryotic serine hydrolase family, designated as Fsh (family of serine hydrolase), identified here for the first time. OVCA2, a potential human tumor suppressor, and DYR-SCHPO, a dihydrofolate reductase from Schizosaccharomyces pombe, are members of this family. Comparing the combined results to results of other proteomic methods showed that only four of the 15 proteins were identified in a recent large-scale, "shotgun" proteomic analysis and eight were identified using a related, but similar, approach (neither identifies function). Only 10 of the 15 were annotated using alternate motif-based computational tools. The results demonstrate the precision derived from combining complementary, function-based approaches to extract biological information from complex proteomes. The chemical proteomics technology indicates that a functional protein is being expressed in the cell, while the computational proteomics technology adds details about the specific type of function and residue that is likely being labeled. The combination of synergistic methods facilitates analysis, enriches true positive results, and increases confidence in novel identifications. This work also highlights the risks inherent in annotation transfer and the use of scoring functions for determination of correct annotations.

Amino Acid Sequence↗
PubMed1985

Relationship between fluidity and ionic permeability of bilayers from natural mixtures of phospholipids.

Proton and calcium permeability coefficients of large unilamellar vesicles made from natural complex mixtures of phospholipids were measured in various conditions and related to membrane fluidity. Permeability coefficients at neutral pH and 25 degrees C were in the range of 10(-4) cm sec-1 and 2.5 X 10(-11) cm sec-1 for protons and calcium, respectively. With the exception of two cases, (H+) greater than 10(-4) M and (Ca2+) greater than 10(-3) M, fluidity increases correspond to permeability increases. Theoretical analysis shows that, for both ions, the measured values of permeability coefficients imply that the permeation process is controlled by the product D1D2 of the diffusion coefficient from the medium into the membrane (D1) by the diffusion coefficient in the membrane (D2). Further analysis of D1 values deduced from combined use of permeability and fluidity data shows that the solubilization should occur in a medium of dielectric constant of about 12, suggesting the involvement of the hydration water of membranes. High proton concentrations, although having virtually no effect on fluidity, trigger the appearance of lateral heterogeneity in membranes, as seen by 31P NMR, and large permeability increases. It is proposed that the main effect of fluidity and/or lateral heterogeneity on permeability may be via the membrane hydration control. We conclude that the current assumption that permeability is controlled by fluidity should be regarded with caution, at least in the case of ions and natural mixtures of phospholipids.

Calcium↗
PubMed1995

Mammalian secreted and cytosolic phospholipase A2 show different specificities for phospholipid molecular species.

Previous studies using phospholipid vesicles containing single molecular species have shown cytosolic phospholipase (85 kDa) (PL) A2 to possess a marked preference for arachidonic acid (20:4n-6)-containing species, while secreted PLA2 (14 kDa) exhibited little acyl chain selectivity. In this study, we have defined the molecular specificity of cytosolic PLA2 using phospholipid vesicles derived from rat liver which contain complex mixtures of molecular species. Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were isolated from rat liver by chloroform and methanol extraction, and solid-phase separation. PC and PE vesicles were hydrolysed by either human recombinant cytosolic or porcine pancreatic PLA2. Molecular species compositions were determined by reverse phase high performance liquid chromatography (HPLC) with post-column fluorescence derivitisation. HPLC analysis after limited hydrolysis demonstrated that the secreted phospholipase A2 showed no significant acyl chain specificity using these phospholipid mixtures. However, the cytosolic enzyme demonstrated a high degree of preference for arachidonic acid-containing species such that there was no hydrolysis of other molecular species. The extent of hydrolysis of PC16:0/20:4 was 1.4-fold greater (P < 0.05, n = 3) than PC18:0/20:4, while PE16:0/20:4 and PE18:0/20:4 were hydrolysed to a similar degree. Under these assay conditions, the cytosolic enzyme showed a preference for PE as compared with PC. This study confirms that cytosolic PLA2 is highly selective for sn-2 20:4n-6-containing phospholipid molecular species even when presented with a complex natural species mixture. This specificity is consistent with the cytosolic enzyme having a primary role in the process of arachidonic release within cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Atmospheric pressure mass spectrometry: a new analytical chemical characterization method for dissolved organic matter in rainwater.

The complex mixture of organic compounds in the atmosphere influences climate, air quality, and ecosystem processes. Atmospheric pressure electrospray ionization mass spectrometry (APESI-MS) was evaluated as a potential tool for direct measurement of the total suite of individual dissolved organic matter (DOM) compounds in rainwater. The APESI-MS response was linear to all DOM compounds of atmospheric significance examined as standard solutions. Urban precipitation samples from New Brunswick, NJ (USA) were analyzed by APESI-MS over the mass-to-charge (m/z) range 50-3,000. Over 95% of the m/z ions detected were in the low m/z range (50-500). Over 300 unique m/z ions were detected across the 11 rainwater samples indicating the complexity of the mixture of DOM in rainwater. Forty percent of the organic bases (positive mode detection) and 22% of the organic acids (negative mode) occurred in at least 6 of the 11 rainwater samples. Ions corresponding to the m/z of carboxylic acids standards (nonanedioic acid; 1,4-butanedicarboxylic acid; pentanedioic acid; hydroxybutanedioic acid; and butanedioic acid) and to reduced N standards (allylurea; caffeine; imidazole; and N-2-propenylurea) occurred in at least one of the 11 rainwater samples. Total dissolved organic carbon (DOC) estimated from the APESI-MS analysis and measured by standard DOC methods were not statistically different.

Air Pollutants↗
PubMed1995

Risk assessment of chemical mixtures from a public health perspective.

Health risk assessment is the practice of evaluating the degree of danger associated with chemical exposure, whether the exposure is intentional (pharmacologic agents, pesticides) or unintentional (industrial/automobile by-products). Chemical exposure can either be to a single chemical or to complex mixtures such as industrial effluents, municipal wastes, jet fuels, gasoline, or mixtures of drinking water contaminants. The mixtures can be simple or complex; partially or completely characterized; and stable or varying in composition. Three different approaches are often used in health risk assessment of chemical mixtures (51 FR 33992-34054). These 3 approaches consist of (a) use of data on the specific mixture of concern; (b) use of data on a similar mixture; and (c) use of data on each component of the mixture. The individual component-based approach is by far the most often used because it allows the individual risks from each component to be combined, usually by dose or response additivity, to calculate an overall risk for the mixture. In addition, several innovative methods, such as the toxicity equivalency factor, relative potency, and even the use of indicator chemicals, are also employed. More recently, a binary weight-of-evidence approach has been proposed to evaluate potential interactions between the various components and to integrate them into the overall toxicity assessment of the mixture. Because no single approach is suitable for assessing the health risk associated with all the exposure scenarios associated with the various types of mixtures, the use of professional judgment is still imperative in conducting health risk assessments.

Drug Interactions↗
PubMed2006

Comprehensive two-dimensional gas chromatography in the analysis of volatile samples of natural origin: a multidisciplinary approach to evaluate the influence of second dimension column coated with mixed stationary phases on system orthogonality.

The study evaluates the influence of selectivity tuning of the stationary phase of the second dimension on the orthogonality of a comprehensive two-dimensional gas chromatography (GC x GC) system. Two different sets of columns, providing independent and semi-independent separation mechanisms were used. The first consisted of a first dimension separating analytes on a volatility basis (i.e. a non-polar polydimethylsiloxane (OV1) column) combined with a second dimension separating by polarity, using columns coated with 100% polyethylene glycol (CW20M), CW20M/OV1 mixtures in ratios of 25-75%, and polydimethylsiloxane, 7% phenyl, 7% cyanopropyl (OV1701). The second set consisted of a first dimension separating analytes on a polarity basis (100% CW20M column) combined with a second dimension separating by volatility, consisting of columns coated with 100% OV1, OV1/CW20M mixtures in ratios of 25-75%, and 100% OV1701. Medium-complexity mixtures of natural origin (i.e. peppermint essential oil and a standard mixture of suspected allergens) consisting of components in a relatively limited range of molecular weights (MW) and volatilities, but belonging to different classes of compounds in a wide range of polarity (mono- and sesquiterpenoids, hydrocarbons and oxygenated compounds) were analysed with the above sets of columns. Different approaches were used to evaluate peak spreading on the GC x GC separation plane and degree of orthogonality of the column sets, namely: (1) a Factor Analysis (FA) approach, estimating the correlation coefficients and spreading angles of the sample components in the two-dimensional chromatographic plane; (2) an Informational Theory (IT) approach, based on determining a group of parameters including: informational entropy, % synentropy and similarity (H); and (3) an approach based on estimating the amount of separation space used, i.e. a practical parameter that directly refers to the experimental separation plane of the GC x GC chromatogram. Results showed that peak spreading in the chromatographic plane, when CW20M and OV1 are combined in different ratios, can be predicted from retention mechanisms, and that the degree of orthogonality measured with different approaches, is consistent with the divergent nature, in terms of polarity of the stationary phases combined in the GC x GC system.

Allergens↗
PubMed2001

MALDI mass spectrometry as a tool for characterizing glycosaminoglycan oligosaccharides and their interaction with proteins.

Matrix-Assisted Laser Desorption Ionization (MALDI) mass spectrometry (MS) has emerged as a powerful, sensitive technique for structural analysis of glycosaminoglycans (GAGs) and their fractions and fragments. Whereas the molecular size of low sulfated or nonsulfated species (such as low-molecular weight [LMW] K5 polysaccharides) can be directly determined up to molecular weights (MWs) of 12 kD, polysulfated species require complexing with a basic polypeptide and at present can be characterized (in terms of both MW and end residues) up to the size of a decasaccharide, even in complex mixtures. MALDI spectra of GAG oligosaccharides in the presence of a complexing protein permit to assess binding to the protein and the presence of multimeric complexes.

Animals↗
PubMedDate not supplied

Genetic toxicity of a mixture of fifteen pesticides commonly found in the Italian diet.

To determine the toxicological effects of complex mixtures of pesticides, we obtained data on 100 pesticide residues in common foods of central Italy. Fifteen pesticides were more regularly detected at higher levels (dithiocarbamates, benomyl/carbendazim, thiabendazole, diphenylamine, chlorthalonil, procymidone, fenarimol, chlorpropham, vinchlozolin, methidathion, chlorpyriphos-ethyl, parathion-methyl, parathion, chlorfenviphos, pirimiphos-ethyl). Using itemized data on daily food consumption in Italy, we calculated that the average exposure for an adult subject was 716 micrograms/day, ranging from 148 micrograms of dithiocarbamates to 1 microgram of pirimiphos-ethyl. We made a mixture of these 15 pesticides at concentrations proportional to the ratio determined in foods and tested it with the Salmonella-microsome assay, with and without metabolic activation with PCB-induced rat liver S9. No mutagenic activity was observed at concentrations up to 500 micrograms/plate. We also tested the same mixture at concentrations ranging from 0.1 to 20 micrograms/ml on human lymphocytes in vitro, and observed a slight but statistically significant increase in sister-chromatid exchanges at 1 microgram/ml. We also administered the mixture in corn oil by gavage to Wistar rats at doses of 1, 10, and 100 micrograms/kg. After 24 hr the ratio between bone marrow polychromatic and normochromatic lymphocytes (a sign of cellular toxicity) was decreased by the exposure, but we did not observe a significant increase in the frequency of micronuclei. We conclude that the pesticide mixture did not have appreciable genotoxic activity in the assays used.

Adult↗
PubMed2001

Producing nature's gene-chips: the generation of peptides for display by MHC class I molecules.

Gene-chips contain thousands of nucleotide sequences that allow simultaneous analysis of the complex mixture of RNAs transcribed in cells. Like these gene-chips, major histocompatibility complex (MHC) class I molecules display a large array of peptides on the cell surface for probing by the CD8(+) T cell repertoire. The peptide mixture represents fragments of most, if not all, intracellular proteins. The antigen processing machinery accomplishes the daunting task of sampling these proteins and cleaving them into the precise set of peptides displayed by MHC I molecules. It has long been believed that antigenic peptides arose as by-products of normal protein turnover. Recent evidence, however, suggests that the primary source of peptides is newly synthesized proteins that arise from conventional as well as cryptic translational reading frames. It is increasingly clear that for many peptides the C-terminus is generated in the cytoplasm, and N-terminal trimming occurs in the endoplasmic reticulum in an MHC I-dependent manner. Nature's gene-chips are thus both parsimonious and elegant.

Aminopeptidases↗
PubMed2005

Screening method for the discovery of potential cancer chemoprevention agents based on mass spectrometric detection of alkylated Keap1.

Natural products are important sources of drugs such as cancer chemopreventive agents, but most assays for the discovery of compounds in natural product extracts are low throughput and provide little information about lead compounds in these complex mixtures. The induction of enzymes such as quinone reductase, glucuronyl transferases, glutathione S-transferases, and sulfotransferases can protect cells against the toxic and neoplastic effects of carcinogens. An increase in the concentration of Nrf2 in the nucleus of a cell upregulates the antioxidant response element and induces the expression of these chemopreventive enzymes. Based on the hypothesis that ubiquitination and proteosome-mediated degradation of Nrf2 in the cytoplasm decreases upon the covalent modification of 1 or more of the 27 cysteine sulfhydryl groups on Keap1 (a protein that sequesters Nrf2 in the cytoplasm) and results in higher Nrf2 levels both in the cytoplasm and in the nucleus, a high-throughput mass spectrometry-based screening assay was designed to detect alkylation of sulfhydryl groups of human Keap1. As an initial high-throughput screening step, matrix-assisted laser desorption time-of-flight mass spectrometry was used to determine whether incubation of Keap1 with a botanical sample produced adducts of Keap1. Test extracts found to form adducts with Keap1 were then incubated with the alternative biological nucleophile glutathione and characterized using LC-UV-MS-MS. After validation of the assay using two model alkylating agents, fractions of an extract of hops (Humulus lupulus L.) from the brewing industry were screened, and several compounds were detected as potential chemopreventive agents. Two of these electrophilic hops constituents were identified as xanthohumol and xanthohumol D. In a subsequent cell-based assay, xanthohumol and xanthohumol D were confirmed to be potent inducers of quinone reductase, and reaction with Keap1 was also confirmed. Therefore, this new mass spectrometric screening assay was demonstrated to facilitate the discovery of chemoprevention agents in complex natural product mixtures.

Alkylation↗
PubMed2005

Photo-induced oxidative cross-linking as a method to evaluate the specificity of protein-ligand interactions.

The isolation of protein-binding synthetic molecules from combinatorial libraries or compound collections is now a common practice in chemical biology. An important, but underdeveloped, aspect of characterizing the binding properties of such molecules is their level of binding specificity. This is often evaluated by simply measuring the equilibrium binding affinity of the compound of interest with its target protein and comparing this value with its affinity to one or a few other purified proteins selected at random. These measurements may not reflect accurately the ability of the compound to seek out its target in a complex mixture of proteins such as a cell extract or serum. A more desirable alternative would be to develop solution assays that measure directly the binding of the molecule of interest to both target and competitor proteins in complex solutions. In this report, we evaluate a rapid and efficient photo-triggered cross-linking reaction for assessing binding specificity of synthetic molecules in protein mixtures. Using peptide-protein complexes, we demonstrate that this reaction provides an unbiased view of the peptide-protein contacts present in solution under a given set of conditions and thus is useful for assessing binding specificity. We also discuss the potential application of this chemistry to the related, but more difficult, problem of the identification of protein targets of bioactive molecules.

Amino Acid Sequence↗
PubMed2005

Oxidative DNA damage from potassium bromate exposure in Long-Evans rats is not enhanced by a mixture of drinking water disinfection by-products.

Public drinking water treated with chemical disinfectants contains a complex mixture of disinfection by-products (DBPs) for which the relative toxicity of the mixtures needs to be characterized to accurately assess risk. Potassium bromate (KBrO(3)) is a by-product from ozonation of high-bromide surface water for production of drinking water and is a rodent carcinogen that produces thyroid, mesothelial, and renal tumors. The proposed mechanism of KBrO(3) renal carcinogenesis involves the formation of 8-oxoguanine (8-oxoG), a promutagenic base lesion in DNA typically removed through base excision repair (BER). In this study, male Long-Evans rats were exposed via drinking water to carcinogenic concentrations of KBrO(3) (0.4 g/L), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (0.07 g/L), chloroform (1.8 g/L), bromodichloromethane (0.7 g/L), or a mixture of all these chemicals at the same concentrations for 3 weeks. Half of one kidney was processed for microscopic examination, and the remaining kidney was frozen for isolation of genomic DNA. Levels of 8-oxoG were measured using HPLC with electrochemical detection in DNA samples incubated with formamidopyrimidine-DNA glycosylase. Aldehydic lesions (e.g. abasic sites) in DNA samples were quantitated using an aldehyde-reactive probe slot-blot assay. Treatment with KBrO(3) produced a measurable increase of 8-oxoG in the kidney, and this effect was greater than that produced by treatment with the DBP mixture. No other single chemical treatment caused measurable increases of 8-oxoG. The mixture effect on the amount of 8-oxoG observed in this study suggests an interaction between chemicals that reduced the generation of oxidative DNA damage. No increases in abasic sites were observed with treatment, but a decrease was apparent in the rats treated with the DBP mixture. These data are consistent with previous studies where chronic exposure to this chemical mixture in drinking water resulted in a less than additive carcinogenic response in Tsc2 mutant Long-Evans rats.

Animals↗
PubMed2005

Genotoxic activity of a technical toxaphene mixture and its photodegradation products in SOS genotoxicity tests.

Toxaphene (CAS No. 800-35-2) is a complex mixture of several hundred components that was used worldwide primarily as an agricultural pesticide with insecticide effects in the second half of the 20th century. In vitro investigations of the genotoxicity and mutagenicity of toxaphene were generally described in the literature, but they provided somewhat equivocal results. We re-evaluated the genotoxicity of technical toxaphene in two prokaryotic systems. The SOS Chromotest showed high sensitivity to toxaphene: three concentrations (40, 20 and 10 mg/l) were clearly positive and the dose-response effect was evident. In the umuC assay, a dose-dependent increase in genotoxic activity was observed at toxaphene concentrations from 2.5 to 40.0 mg/l, but these results were found to be not significant. The genotoxicity of toxaphene and its photodegradation products after UV-irradiation (3-6-9 h) at concentrations ranging from 7.5 to 60.0 mg/l was also examined in this study. An irradiated solution of technical toxaphene after 3 h showed no significant evidence of bacterial growth inhibition. However, exposure of Salmonella to 6 h UV-irradiated toxaphene showed a toxic effect compared with the negative control. After 9 h irradiation, a decrease of bacterial growth was observed. Activity of beta-galactosidase in the presence of a toxaphene solution was significantly increased after 6 and 9 h irradiation, reaching values that were 2.4- and 3.1-fold higher, respectively, than the control, which exceeded the criteria of significant genotoxicity. These results show that while technical toxaphene is a weak, direct-acting mutagen in some bacterial tests, a dose-dependent toxicity and genotoxicity of its photoproducts could be conclusively demonstrated by the umuC test.

Animals↗
PubMed1998

Mutagenic interactions of model chemical mixtures.

Although current methodology for human health risk assessment assumes additive interactions among the contaminants of a complex mixture, chemical interactions may occur which produce synergistic or antagonistic effects. In this study, the mutagenic response of three f2p4l compounds, benzo(a)pyrene (B(a)P), pentachlorophenol (PCP) and 2,4,6-trinitrotoluene (TNT), were tested individually and in binary and tertiary solutions, using the Salmonella/microsome assay with each of three bacterial tester strains (TA97a, TA98, and TA100). For all strains, B(a)P was mutagenic with metabolic activation (Arochlor 1254-induced Sprague-Dawley rat liver S9 fraction), TNT was mutagenic without metabolic activation, and pentachlorophenol was inactive both with and without metabolic activation. In binary and tertiary solutions, pentachlorophenol had no effect on the mutagenicity of B(a)P or TNT, independent of metabolic activation. For strain TA97a, the mutagenicity of B(a)P with metabolic activation was slightly decreased in the presence of TNT; the mutagenicity of TNT without metabolic activation was slightly decreased in the presence of B(a)P and PCP; and the mutagenicity of the tertiary solution (496 revertants/10 ug) with metabolic activation was lower than the mutagenicity of B(a)P alone (729 revertants/10 ug). The mutagenicity of B(a)P in strain TA98 with activation was inhibited by the addition of TNT. Studies conducted using several concentrations of TNT or B(a)P indicate that the inhibition of B(a)P mutagenicity was increased as the concentration of TNT increased. Assays performed using four concentrations of S9 indicated the inhibition of B(a)P mutagenicity was relatively unaffected by the level of S9. The data suggest that an interaction in the presence of TNT limits the concentration of B(a)P that is capable of reaching or binding with bacterial DNA.

Animals↗
PubMed1990

Rapid, sensitive analysis of protein mixtures by mass spectrometry.

We have developed a method for determining the molecular masses of proteins in complex mixtures by mass spectrometry. The method has the capacity to examine the components of mixtures without using any chromatographic separation steps and will tolerate relatively large amounts of buffers and inorganic contaminants. It allows the simultaneous determination of protein molecular masses from 1 to 40 kDa with an accuracy of +/- 0.01% and above 40 kDa with reduced accuracy. The lower limit for practical detection of a protein is a concentration of approximately 0.1 microM, and less than 1 microliter of such a solution is consumed. The analysis is very fast: less than 15 min is necessary to perform the complete analysis, including sample preparation, introduction into the mass spectrometer, mass spectrum collection, and data reduction. The mass spectrum that is obtained does not require elaborate interpretation because there is no fragmentation of the ionized protein (or protein subunit) molecule. Therefore, there is a one-to-one correspondence between the peaks in the mass spectrum and the proteins present in the original mixture. The spectra assume the appearance of chromatograms, with the abscissa being mass-to-charge ratio rather than chromatographic retention time.

Animals↗