Individual Amino Acids (individual + amino_acids)

Distribution by Scientific Domains

Selected Abstracts

Amino acid 15N in long-term bare fallow soils: influence of annual N fertilizer and manure applications

R. Bol
Summary Long-term dynamics of amino acids (AAs), from a bare fallow soil experiment (established in 1928 at INRA-Versailles, France), were examined in unamended control (Con) plots and plots treated with ammonium sulphate (Amsul), ammonium nitrate (Amnit), sodium nitrate (Nanit) or with animal manure (Man). Topsoil (0,25 cm) from 1929, 1963 and 1997 was analysed for C, N and 15N content and distribution of 18 amino acids recovered after acid hydrolysis with 6 m HCl. With time, soil N, C and AA content were reduced in Con, Amsul, Amnit and Nanit, but increased in Man. However, the absolute N loss was 3,11 times larger in Man than Nanit, Amsul, Amnit and Con, due to the much higher N annual inputs applied to Man. From 1929 to 1997 in Con, Amsul, Amnit and Nanit the whole soil and non-hydrolysable-N pool ,15N increased associated with the loss of N (indicative of Rayleigh 15N/14N fractionation). No ,15N change from 1929 to 1997 was found in the hydrolysable AA-N (HAN) pool. Fertilizer N inputs aided stabilization of soil AA-N, as AA half-life in the mineral N fertilizer treatments increased from 34 years in 1963 to 50 years in 1997. The ,15N values of alanine and leucine reflected both source input and 15N/14N fractionation effects in soils. The ,15N increase of ornithine (,6,) was similar to the whole soil. The ,15N change of phenylalanine in Con (decrease of 7,) was related to its proportional loss since 1929, whereas for Amsul, Amnit, Nanit and Man it was associated with isotope effects caused by the fertilizer inputs. However, the soil ,15N value of most individual amino acids (IAAs) did not significantly change over nearly 70 years, even with mineral or organic N inputs. We conclude for these bare fallow systems that: (i) ,15N changes in the whole soil and non-hydrolysable AA pool were solely driven by microbial processes and not by the nature of fertilizer inputs, and (ii) without plant inputs, the ,15N of the HAN pool and (most) IAAs may reflect the influence of plant,soil interactions from the previous (arable cropping) rather than present (fallow) land use on these soil ,15N values. [source]

Analysis of Usp DNA binding domain targeting reveals critical determinants of the ecdysone receptor complex interaction with the response element

FEBS JOURNAL, Issue 13 2001
Iwona Grad
The steroid hormone, 20-hydroxyecdysone (20E), directs Drosophila metamorphosis via a heterodimeric receptor formed by two members of the nuclear hormone receptors superfamily, the product of the EcR (EcR) and of the ultraspiracle (Usp) genes. Our previous study [Niedziela-Majka, A., Kochman, M., O,yhar, A. (2000) Eur. J. Biochem.267, 507,519] on EcR and Usp DNA-binding domains (EcRDBD and UspDBD, respectively) suggested that UspDBD may act as a specific anchor that preferentially binds the 5, half-site of the pseudo-palindromic response element from the hsp27 gene promoter and thus locates the heterocomplex in the defined orientation. Here, we analyzed in detail the determinants of the UspDBD interaction with the hsp27 element. The roles of individual amino acids in the putative DNA recognition , helix and the roles of the base pairs of the UspDBD target sequence have been probed by site-directed mutagenesis. The results show how the hsp27 element specifies UspDBD binding and thus the polar assembly of the UspDBD/EcRDBD heterocomplex. It is suggested how possible nucleotide deviations within the 5, half-site of the element may be used for the fine-tuning of the 20E-response element specificity and consequently the physiological response. [source]

Amino acid ingestion and glucose metabolism,A review

IUBMB LIFE, Issue 9 2010
Mary C. Gannon
Abstract Interest in the effect of proteins or amino acids on glucose metabolism dates back at least a century, largely because it was demonstrated that the amino acids from ingested protein could be converted into glucose. Indeed, these observations influenced the dietary information provided to people with diabetes. Subsequently it was shown that ingested protein did not raise the blood glucose concentration. It also was shown that proteins could stimulate a rise in insulin and glucagon but the response to various proteins was different. In addition, it was shown that individual amino acids also could stimulate a rise in insulin and in glucagon concentrations. When individual amino acids are ingested by normal subjects, there is an ordering of the insulin and glucagon responses. However, the order is not the same for insulin and glucagon. In addition, the metabolic response cannot be predicted based on the functional groups of the amino acids. Thus, empirical prediction of the metabolic response to ingested single amino acids is not possible. © 2010 IUBMB IUBMB Life, 62(9): 660,668, 2010 [source]

Yttrium oxide (Y2O3) as an inert marker in digestibility studies with dogs, blue foxes and mink fed diets containing different protein sources

S. G. Vhile
Summary The study evaluated the use of yttrium oxide (Y2O3) as an inert marker in studies of apparent total tract digestibility in dogs, blue foxes and mink. Comparison was made with total faecal collection, and use of chromic oxide (Cr2O3) as marker respectively. Four experimental diets were added 0.1 g/kg yttrium oxide and 10 g/kg chromic oxide and fed to four animals of each species. Faecal recovery of yttrium oxide was 94.4% (SEM ± 1.0), and of chromic oxide 105.8% (SEM ± 1.5). The digestibilities of dry matter, crude protein, crude fat, starch and total carbohydrates obtained by total collection and yttrium oxide as marker showed close similarity, and in most cases not significant differences, independent of species and diets. In dogs, overall digestibilities of main nutrients with chromic oxide as marker were not significantly different from overall means obtained with yttrium oxide (p > 0.05). Overall digestibility of dry matter, crude protein and total carbohydrates in blue foxes and mink was significantly higher with chromic oxide than with yttrium oxide (p < 0.05). In dogs and blue foxes, digestibilities of individual amino acids determined by use of yttrium oxide were not different from values obtained using total collection of faeces, both within diets and for overall mean (p > 0.05). Overall amino acid digestibilities in dogs determined with chromic oxide as marker were similar to corresponding figures for yttrium oxide, whereas use of chromic oxide resulted in significantly higher digestibilites for a number of amino acids compared with yttrium oxide in foxes and mink (p < 0.05). The digestibilities of most main nutrients and amino acids revealed no interaction between diet and method (p > 0.05). The study showed that yttrium oxide can be used in low concentration in the feed, and allows high accuracy of analyses and thereby precise digestibility determination. It is concluded that yttrium oxide is an alternative inert marker to chromic oxide in the studied species. [source]

Amino Acid Absorption in Portal Blood After Duodenal Infusions of a Soy Protein Hydrolysate Prepared by a Novel Soybean Protease D3

Tomohiro Kodera
ABSTRACT:, The intestinal absorption of amino acids from decapeptide was investigated in rats under unrestrained conditions. The soy protein hydrolysate utilized in the experiment was produced by a novel soybean protease D3. The enzymatic features of protease D3 showed high homology with cathepsin L and cathepsin K and the average molecular weight of D3 hydrolysate is approximately 1200. We compared the intestinal absorption of D3 hydrolysate in portal blood with that of an amino acids mixture and soy protein with the same amino acid composition by determining the concentration of individual amino acids after a single administration of a nitrogen source. The absorptive velocity and intensity of each amino acid were calculated from its rate of elevation in the portal blood. And in most cases, these were higher in the D3 hydrolysate than in amino acids mixture and protein. The proportion of the amount of each amino acid absorbed in portal blood from D3 hydrolysate was much more like the composition of the administrated amino acids than like that from the amino acids mixture. The result of in vitro digestion assay indicated that D3 hydrolysate was hydrolyzed easier than the hydrolysates produced by microbial proteases. This is the first report to demonstrate that the D3 hydrolysate, which contains decapeptide as a dominant fraction, was more rapidly utilized than the amino acids mixture and protein as is the case with di-, tripeptides. This suggested that this hydrolysate could be available for nutraceutical use as well as use in nutritious foods for athletes and patients. [source]

A study to assess the cross-reactivity of cellulose membrane-bound peptides with detection systems: an analysis at the amino acid level

Carsten C. Mahrenholz
Abstract The growing demand for binding assays to study protein,protein interaction can be addressed by peptide array-based methods. The SPOT technique is a widespread peptide-array technology, which is able to distinguish semi-quantitatively the binding affinities of peptides to defined protein targets within one array. The quality of an assay system used for probing peptide arrays depends on the well-balanced combination of screening and read-out methods. The former address the steady-state of analyte capture, whereas the latter provide the means to detect captured analyte. In all cases, however, false-positive results can occur when challenging a peptide array with analyte or detecting captured analyte with label conjugates. Little is known about the cross-reactivity of peptides with the detection agents. Here, we describe at the amino acid level the potential of (i) 5-(and 6)-carboxytetramethylrhodamine (5(6)-TAMRA), (ii) fluoresceinisothiocyanate in form of the peptide-bound fluorescein-substituted thiourea derivative (FITC), and (iii) biotin/streptavidin-POD to cross-react with individual amino acids in a peptide sequence. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd. [source]

Recalcitrant soil organic materials mineralize more efficiently at higher temperatures

Roland Bol
Abstract As concentrations of atmospheric CO2 increase, it is important to know whether this may result in feedbacks that could modify the rate of increase of CO2 in the atmosphere. Soil organic matter (SOM) represents one of the largest pools of C and mineralization rates are known to be temperature dependent. In this study, we investigated whether different OM fractions present in a forest soil (F/A1 horizon) would respond in a similar manner to elevated temperatures. We examined the trends in isotopic content (12C, 13C, and 14C) of soil respired CO2 at various temperatures (10, 20, and 35 0C) over a two year period in the laboratory. We also examined the total C, total N, and C,:,N ratio in the remaining soil and isolated humic fractions, and the distribution of the individual amino acids in the soil after 5 years of laboratory incubation at the various temperatures. We found that the rate at which C mineralization increases with temperature was occasionally greater than predicted by most models, more C from recalcitrant OM pools being mineralized at the higher temperature. This confirmed that the relationship between soil organic matter decomposition and temperature was complex and that the different pools of organic matter did respond in differing ways to elevated temperatures. Rekalizitrante organische Bodensubstanz mineralisiert bei höheren Temperaturen effizienter Vor dem Hintergrund ansteigender atmosphärischer CO2 -Konzentrationen gewinnt die Erforschung möglicher Rückkopplungs-Mechanismen zunehmend an Bedeutung. Die organische Bodensubstanz stellt eines der größten terrestrischen C-Reservoirs dar. Die Rate der C-Mineralisation aus der organischen Bodensubstanz gilt allgemein als temperaturabhängig. In der hier vorgestellten Untersuchung sollte geprüft werden, ob verschiedene Fraktionen der organischen Bodensubstanz eines Waldstandortes (F/A1-Horizont) ähnlich stark auf erhöhte Temperaturen reagieren. Über einen Zeitraum von zwei Jahren wurde unter Laborbedingungen die Veränderung der Isotopen-Gehalte (12C, 13C und 14C) des bei verschiedenen Temperaturen (10, 20 und 35 °C) inkubierten Bodens untersucht. Ebenfalls erfasst wurden Gesamt-C, Gesamt-N und C,:,N-Verhältnis im Gesamt-Boden und in isolierten Humus-Fraktionen sowie das Verteilungsmuster der Aminosäuren im Boden nach fünfjähriger Inkubationsdauer. Die Ergebnisse zeigen, dass die temperaturbedingte Erhöhung der Mineralisationsrate in einigen Fällen deutlich stärker ausgeprägt ist, als anhand von Modellberechnungen erwartet wurde. Ursache hierfür ist unter erhöhten Temperaturen intensivere C-Mineralisation aus rekalzitranter organischer Bodensubstanz. Dies bestätigt unsere Vermutung, dass es keinen einfachen Zusammenhang zwischen Mineralisationsrate und Temperatur gibt, da verschiedene Humusbestandteile unterschiedlich auf erhöhte Temperaturen reagieren. [source]

Tail Muscle Free Amino Acid Concentration of Pacific White Shrimp, Litopenaeus vannamei, Fed Diets Containing Protein-bound versus Crystalline Amino Acids

Joe M. Fox
Tail muscle tissue free amino acids (FAA) concentration is reported for subadult (4.3 g) Litopenaeus vannamei fed diets containing only protein-bound amino acids, crystalline lysine as a supplement to protein-bound lysine, and only crystalline amino acids (CAA). FAA were determined in shrimp at 0.00, 0.25, 0.5, 1, 2, 4, and 8 h postfeeding. Highest total tissue concentrations of essential amino acids and individual amino acids were typically observed 4 h postfeeding for shrimp fed intact and crystalline lysine-supplemented feeds. Those shrimp offered diets containing only CAA showed no tissue maxima. Similar uptake patterns for lysine shown by shrimp fed the intact and crystalline lysine-supplemented diet indicate the potential use of small amounts of crystalline lysine in shrimp feeds. [source]

Characterization of point mutations in the cdtA gene of the cytolethal distending toxin of Actinobacillus actinomycetemcomitans

Linsen Cao
Summary The Cdt is a family of gram-negative bacterial toxins that typically arrest eukaryotic cells in the G0/G1 or G2/M phase of the cell cycle. The toxin is a heterotrimer composed of the cdtA, cdtB and cdtC gene products. Although it has been shown that the CdtA protein subunit binds to cells in culture and in an enzyme-linked immunosorbent assay (CELISA) the precise mechanisms by which CdtA interacts with CdtB and CdtC has not yet been clarified. In this study we employed a random mutagenesis strategy to construct a library of point mutations in cdtA to assess the contribution of individual amino acids to binding activity and to the ability of the subunit to form biologically active holotoxin. Single unique amino acid substitutions in seven CdtA mutants resulted in reduced binding of the purified recombinant protein to Chinese hamster ovary cells and loss of binding to the fucose-containing glycoprotein, thyroglobulin. These mutations clustered at the 5,- and 3,-ends of the cdtA gene resulting in amino acid substitutions that resided outside of the aromatic patch region and a conserved region in CdtA homologues. Three of the amino acid substitutions, at positions S165N (mutA81), T41A (mutA121) and C178W (mutA221) resulted in gene products that formed holotoxin complexes that exhibited a 60% reduction (mutA81) or loss (mutA121, mutA221) of proliferation inhibition. A similar pattern was observed when these mutant holotoxins were tested for their ability to induce cell cycle arrest and to convert supercoiled DNA to relaxed and linear forms in vitro. The mutations in mutA81 and mutA221 disrupted holotoxin formation. The positions of the amino acid substitutions were mapped in the Haemophilus ducreyi Cdt crystal structure providing some insight into structure and function. [source]

Assessment of protein nutritional quality and effects of traditional processes: A comparison between Ethiopian quality protein maize and five Ethiopian adapted normal maize cultivars

Habtamu Fufa
Abstract The present study was designed to quantitatively measure and compare the levels and variations of total protein, individual amino acids, and computed protein efficiency ratio (C-PER) in raw and traditionally processed products of one recently released quality protein maize (QPM BH542) with four high-yield maize hybrids, namely flint BH660, semi-dent BH140, Pioneer 30H83, and Pioneer 30G97, as well as one local maize cultivar. The total protein content was variable among the cultivars ranging from 7% for BH660 to 8.6% for Pioneer 30H83, 8.9% for BH140, 9.8% for QPM BH542, 10.1% for local maize cultivar, and 11.8% for Pioneer 30G97, respectively. However, the QPM BH542 maize protein proved to be higher in nutritional quality than common maize proteins because it contained 30% to 82% more lysine, higher levels of arginine, tryptophan, histidine, threonine, cysteine, and valine. As a result, the QPM BH542 amino acid profile gives a good balance of total essential amino acids, limited only in lysine, and has a C-PER ratio of 2.2 compared to 1.14, 1.2, 1.4, 1.66, and 1.67 for Pioneer 30G97, local, BH-140, BH660, and Pioneer 30H83, respectively. The various traditional processes of maize have no significant effect on the protein nutritional quality of the new quality protein maize. Hence, the widely dissemination of it in agricultural cultivation as well as consumption by the general population is recommended. [source]

Amino acid budgets in three aphid species using the same host plant

J. P. Sandström
Abstract. Nutrient provisioning in aphids depends both on the composition of ingested phloem sap and on the biosynthetic capabilities of the aphid and its intracellular symbionts. Amino acid budgets for three aphid species, Rhopalosiphum padi (L.), Schizaphis graminum (Rondani) and Diuraphis noxia (Mordvilko), were compared on a single host plant species, wheat Triticum aestivum L. Ingestion of amino acids from phloem, elimination of amino acids in honeydew, and the content of amino acids in aphids tissue were measured. From these values, ingestion rates were estimated and compared to honeydew and to estimated composition of aphid proteins. Ingestion rate was lowest in D. noxia due to low growth rate and low honeydew production; intermediate in S. graminum due to higher growth rate and intermediate honeydew production; and highest in R. padi, which had the highest rates for both variables. Both D. noxia and S. graminum induced increases in the amino acid content of ingested phloem. These changes in phloem content, combined with differences in ingestion rates, resulted in large differences among aphids in estimated rates of ingestion of individual amino acids. In honeydew, most essential amino acids were found in low amounts compared with the amounts ingested, especially for methionine and lysine. A few amino acids (arginine, cystine, histidine and tryptophan) were more abundant in honeydew of some aphids, suggesting oversupply. Aphid species differed in the composition of free amino acids in tissue but showed very similar composition in protein, implying similar requirements among the aphids. In R. padi and D. noxia, most essential amino acids were ingested in amounts insufficient for growth, implying dependence on symbiont provisioning. In S. graminum, most amino acids were ingested in amounts apparently sufficient for growth. [source]

Quantitative evaluation of marine protein contribution in ancient diets based on nitrogen isotope ratios of individual amino acids in bone collagen: An investigation at the Kitakogane Jomon site

Yuichi I. Naito
Abstract Nitrogen stable isotopes analysis of individual bone collagen amino acids was applied to archeological samples as a new tool for assessing the composition of ancient human diets and calibrating radiocarbon dates. We used this technique to investigate human and faunal samples from the Kitakogane shell midden in Hokkaido, Japan (5,300,6,000 cal BP). Using compound-specific nitrogen isotope analysis of individual amino acids, we aimed to estimate i) the quantitative contribution of marine and terrestrial protein to the human diet, and ii) the mean trophic level (TL) from which dietary protein was derived from marine ecosystems. Data were interpreted with reference to the amino acid trophic level (TLAA) model, which uses empirical amino acid ,15N from modern marine fauna to construct mathematical equations that predict the trophic position of organisms. The TLAA model produced realistic TL estimates for the Kitakogane marine animals. However, this model was not appropriate for the interpretation of human amino acid ,15N, as dietary protein is derived from both marine and terrestrial environments. Hence, we developed a series of relevant equations that considered the consumption of dietary resources from both ecosystems. Using these equations, the mean percentage of marine protein in the Kitakogane human diet was estimated to be 74%. Although this study is one of the first systematic investigations of amino acid ,15N in archeological bone collagen, we believe that this technique is extremely useful for TL reconstruction, palaeodietary interpretation, and the correction of marine reservoir effects for radiocarbon dating. Am J Phys Anthropol 143:31,40, 2010. © 2010 Wiley-Liss, Inc. [source]

Association of the , nucleotide with codon bias, amino acid usage and expressivity: differences between Bacillus subtilis and Escherichia coli

APMIS, Issue 10 2003
By measuring the non-randomness in Shine-Dalgarno regions it was recently shown that the compositional non-randomness peaks approximately 10 nucleotides upstream of the start codons. This position, termed the , position, was furthermore shown to be associated with certain characteristics of the gene/protein and start codon usage. This raises the question whether codon usage in general is associated with the , position. In this study, the connection between the , nucleotide and general codon usage, both gene-wide and at the level of individual amino acids, was studied in Eschericia coli and Bacillus subtilis. E. coli but not B. subtilis shows a strong general association between the , position and codon usage bias. In both species, the genes with higher expressivity show stronger conservation in the Shine-Dalgarno region compared to the genes with lower expressivity. [source]

Strong associations between gene function and codon usage

APMIS, Issue 9 2003
The association between codon usage and gene function was analyzed in the complete genomes of Eschericia coli, Bacillus subtilis, Lactococcus lactis and Campylobacter jejuni, using the functional annotation provided by NCBI. Two distinctly different ways of quantifying codon usage were used in the analysis. By using contingency tables it was found that for most amino acids a highly significant association with gene function exists for all species, indicating that codon usage at the level of individual amino acids is generally closely coordinated with gene function. By computing the effective number of codons in the annotated genes and comparing the median values in groups of different gene functions it was shown for all species that codon bias gene by gene also differs. [source]

Nutrients apparent digestibility coefficients of selected protein sources for juvenile Siberian sturgeon (Acipenser baerii Brandt), compared by two chromic oxide analyses methods

Abstract Apparent digestibility coefficients (ADCs) of dry matter (ADCd), crude protein (ADCp), energy (ADCe) and amino acids in selected feedstuffs were determined for juvenile Siberian sturgeon (8.38 ± 0.20 g). The tested feedstuffs were fishmeal (FM), meat and bone meal (MBM), poultry by-product meal, hydrolysed feather meal, fermented feather meal solvent-extracted cottonseed meal and soybean meal. ADCs were determined using a reference diet and test diets at 7 : 3 ratios with 5 g kg,1 chromic oxide (Cr2O3) as an inert marker. Fish were reared in a recirculating system and fed to apparent satiation five times daily. Cr2O3 in diets and faeces samples were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) and acid-digestion colorimetry (AC) methods, respectively. The results showed that ICP-AES method was more accurate for Cr2O3 determination than AC method, and the results determined by ICP-AES method were used in this study. ADCd and ADCp of seven tested ingredients were lowest for MBM (59.1 and 84.5%) and highest for FM (79.9 and 94.5%); ADCe of tested ingredients were from 71.8% for SECM to 93.2% for FM. ADCs of amino acid in test ingredients followed similar trend to the ADCp. The ADCs of individual amino acids varied from 61.6% (histidine in MBM) to 98.8% (valine in FM). [source]

Estimating digestible protein requirements of silver perch, Bidyanus bidyanus Mitchell

G L Allan
Abstract In this study, we estimated requirements for digestible protein, using intact protein sources, at one digestible energy content. Using digestibility data for silver perch (Bidyanus bidyanus Mitchell) for a large number of ingredients, we formulated a ,summit' diet to contain between 1.4 and 1.8 times the ,expected requirements' for digestible essential amino acids (based on requirements for channel catfish, Ictalurus punctatus Rafinesque). A ,diluent' diet was formulated to contain 0.4,0.5 times the expected requirements of digestible essential amino acids. Both ,summit' and ,diluent' diets contained similar digestible energy (14.7 MJ digestible energy kg,1 for the summit and 13.4 MJ digestible energy kg,1 for the diluent). Six diets were prepared with the following amounts of summit,diluent diets: 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100. A practical diet widely used by commercial farmers was also included as a control. Ten juvenile fish (2.1,2.6 g) were stocked into each experimental 70-L acrylic aquarium, and each dietary treatment was randomly assigned to five replicate aquaria. Fish were fed twice daily to apparent satiation for 54 days. Final individual fish weight ranged from 4,15.5 g. Results were analysed using intersecting linear regression analysis. The optimum digestible dietary protein for diets with 13.4,14.7 MJ digestible energy kg,1, after which protein deposition did not increase significantly, was 28%. Although this study did not determine requirements for individual amino acids, for diets with the digestible energy content used here, requirements for individual amino acids obviously did not exceed the content in the 28% protein diet. These contents are useful as an estimate of ,recommended levels' for silver perch diets with 13.4,14.7 MJ digestible energy kg,1. The proximate composition of fish was affected by diet. Whole body protein and moisture increased, whereas lipid content decreased with increasing dietary protein content (and increasing protein,energy ratio and decreasing lipid). Fish size was also affected by diet; however, the changes in whole carcass proximate composition also occurred for fish fed diets 60:40, 80:20 and the summit diet which were a similar final weight. [source]

An accessible two-dimensional solution nuclear magnetic resonance experiment on human ubiquitin,

David Rovnyak
Abstract Solution-state nuclear magnetic resonance (NMR) is an invaluable tool in structural and molecular biology research, but may be underutilized in undergraduate laboratories because instrumentation for performing structural studies of macromolecules in aqueous solutions is not yet widely available for use in undergraduate laboratories. We have implemented an experiment that is ideal for more commonly available 4.8,7.0 Tesla, double-channel NMR instruments that would not usually be used for biomolecular NMR work. We analyzed a commercially available, 15N-enriched human ubiquitin sample with a two-dimensional correlation experiment using indirect 1H evolution and direct 15N detection, which produced spectra with high resolution on a spectrometer operating at 7.0 Tesla (300 MHz 1H resonance frequency). The simplicity of the experiment makes it possible to be configured by undergraduate students with minimal supervision from the instructor. Students gain experience in acquiring multidimensional biomolecular NMR experiments, confirm that ubiquitin is stably folded, and observe the correspondence between specific signals and individual amino acids in ubiquitin. [source]

Tunable DNA Cleavage by Intercalating Peptidoconjugates

CHEMBIOCHEM, Issue 5 2006
Kerry P. Mahon Jr.
Abstract The properties of a novel family of peptide-based DNA-cleavage agents are described. Examination of the DNA-cleavage activities of a systematic series of peptide,intercalator conjugates revealed trends that show a strong dependence on peptide sequence. Conjugates differing by a single residue displayed reactivities that varied over a wide range. The cleavage activity was modulated by the electrostatic or steric qualities of individual amino acids. Isomeric conjugates that differed in the position of the tether also exhibited different reactivities. The mechanism of DNA cleavage for these compounds was also probed and was determined to involve hydrogen-atom abstraction from the DNA backbone. Previous studies of these compounds indicated that amino acid peroxides were the active agents in the cleavage reaction; in this report, the chemistry underlying the reaction is characterized. The results reported provide insight into how peptide sequences can be manipulated to produce biomimetic compounds. [source]