(Table 2) Concentrations and D/L values for three amino acids in bulk foraminifera from ODP Sites 182-1126 and 182-1127

A number of studies have shown that methanogens are active in the presence of sulfate under some conditions. This phenomenon is especially exemplified in carbonate sediments of the southern Australian continental margin. Three sites cored during Ocean Drilling Program (ODP) Leg 182 in the Great Australian Bight have high concentrations of microbially-generated methane and hydrogen sulfide throughout almost 500 m of sediments. In these cores, the sulfate-reducing and methanogenic zones overlap completely; that is, the usual sulfate-methane transition zone is absent. Amino acid racemization data show that the gassy sediments consist of younger carbonates than the low-gas sites. High concentrations of the reduced gases also occur in two ODP sites on the margin of the Bahamas platform, both of which have similar sedimentary conditions to those of the high-gas sites of Leg 182. Co-generation of these reduced gases results from an unusual combination of conditions, including: (1) a thick Quaternary sequence of iron-poor carbonate sediments, (2) a sub-seafloor brine, and (3) moderate amounts of organic carbon. The probable explanation for the co-generation of hydrogen sulfide and methane in all these sites, as well as in other reported environments, is that methanogens are utilizing non-competitive substrates to produce methane within the sulfate-reducing zone. Taken together, these results form the basis of a new model for sulfate reduction and methanogenesis in marine sediments. The biogeochemical end-members of the model are: (1) minimal sulfate reduction, (2) complete sulfate reduction followed by methanogenesis, and (3) overlapping sulfate reduction and methanogenesis with no transition zone.

Granulometry, geochemistry, amino acids, radiocarbon ages and paleomagnetics of samples from Heidemann Valley

A Pliocene (2.6-3.5 Ma) age is determined from glacial sediments studied in a 20m long, 4 m deep trench excavated in Heidemann Valley, Vestfold Hills, East Antarctica. The age determination is based on a combined study of amino acid racemization, diatoms, foraminifera, and magnetic polarity, and supports earlier estimates of the age of the sedimentary section; all are beyond 14C range. Four till units are recognized and documented, and 16 subunits are identified. All are ascribed to deposition during a Late Pliocene glaciation that was probably the last time the entire Vestfold Hills was covered by an enlarged East Antarctic Ice Sheet (EAIS). Evidence for other more recent glacial events of the 'Vestfold Glaciation' may have been due to lateral expansion of the Sorsdal Glacier and limited expansion of the icesheet margin during the Last Glacial Maximum rather than a major expansion of the EAIS. The deposit appears to correlate with a marine deposition event recorded in Ocean Drilling Program Site 1166 in Prydz Bay, possibly with the Bardin Bluffs Formation of the Prince Charles Mountains and with part of the time represented in the ANDRILL AND-1B core in the Ross Sea.

(Table 1) Concentrations of amino acids in sediments from DSDP Site 68-502

In this chapter, we will report on the amino acids in the total acid hydrolysate of eight sediment samples from Leg 68 Site 502. This site was located on a topographic high at a depth of 3051 meters in the Colombian Basin of the western Caribbean Sea. Four holes were cored at the site by means of the hydraulic piston corer to a maximum sediment depth of 218 meters. The composite section is a virtually continuous, undisturbed sediment record covering almost 8 million years from the Holocene to late Miocene. Age estimates for the section are based on excellent magnetostratigraphic and biostratigraphic records. Four lithostratigraphic units (A, B, C, and D) were recognized, based on differences in color and content of clay, ash, foraminifers, and siliceous microfossils (Prell, Gardner, et al., 1980): A, yellowish brown to light brownish gray foraminifer-bearing (> 10%) nannofossil marl; B, gray to olive gray foraminifer-bearing nannofossil marl with occasional ash beds; C, light gray to dark greenish gray calcareous clay and foraminifer-bearing (< 10%) nannofossil marl; D, pale green to grayish green calcareous, ash-bearing clay with siliceous microfossils. The calcium carbonate content of these sediments increases from about 27 to about 49% from late Miocene to middle Pliocene (about 3.6 Ma) and remains uniform at about 48 to 50% from that time throughout the Quaternary. The eight sediment samples for amino acid analyses came from the third (502B) and fourth (502C) holes at Site 502. Samples ranged in sub-bottom depth from 4.3 to 225 meters spanning time from 0.3 to 7.7 Ma.

A combination of amino acids and caffeine enhances sprint running capacity in a hot, hypoxic environment.

Understanding the cation specific effects on the aqueous solubility of amino acids: from mono to polyvalent cations

The interactions established by mono and polyvalent cations in natural media have important implications on the structure formation, function and physico-chemical behavior of biomolecules, playing therefore a critical role in biochemical processes. In order to further elucidate the molecular phenomena behind the cation specific effects in biological environments, and clarify the influence of the charge of the ions, solubility measurements and molecular dynamics simulations were performed for aqueous solutions of three amino acids (alanine, valine and isoleucine), in the presence of a series of inorganic salts comprising mono-, di- and trivalent cations (LiCl, Li2SO4, K2SO4, CaCl2, AlCl3 and Al-2(SO4)(3)). The evidence gathered indicates that the mechanism by which (salting-in inducing) polyvalent cations affect the solubility of amino acids in aqueous solutions is different from that of monovalent cations. A consistent and refined molecular description of the effect of the cation on the solubility of amino acids based on specific interactions of the cations with the negatively charged moieties of the biomolecules is here proposed.

Volumetric interactions of a series of α-amino acids in aqueous magnesium chloride solutions at 278.15, 288.15, 298.15, and 308.15 K

In this work, the partial molar volumes of glycine, l-alanine, l-valine, l-serine, and l-threonine in aqueous solutions of magnesium chloride at 0.0, 0.1, 0.3, 0.7, and 1.0 molal are addressed between 278.15 and 308.15 K. Volumes of transfer were obtained, following the rank serine > glycine a parts per thousand threonine > alanine > valine. Differently, the hydration numbers follow the sequence serine > valine > alanine > threonine > glycine, and dehydration of the amino acids is observed, rising the temperature or salt molality. The data suggest that interactions are mainly pairwise, between the ions and charged/hydrophilic groups of the amino acids. Within the Friedman and Krishnan formalism, a group-contribution scheme has been successfully applied to the pairwise volumetric interaction coefficient. Finally, the dehydration effect of MgCl2 on glycine, alanine, and serine has been predicted applying empirical correlations developed before, showing satisfactory results.

Apparent digestibility of dry matter, crude protein, and amino acids of six rendered by-products in juvenile Litopenaeus vannamei

Apparent digestibility coefficients (ADC) of dry matter, crude protein (CP), and amino acids (AA) were evaluated in diets with six rendered by-products used to feed juvenile Pacific white shrimp: two poultry meals (poultry meal 1, 69% CP; poultry meal 2, 72% CP), two feather meals (89% CP), one blood meal (96% CP), and one pork meal (57% CP). Experimental diets were formulated with 30% of the test ingredient and 70% of a commercial diet supplemented with 1% of chromium oxide as inert marker. AA contents in ingredients, diets, leached diets, and feces were determined by high performance liquid chromatography. Preprandial AA losses attributed to leaching were higher in the blood meal diet (15%) and pork meal diet (10%). Poultry meal diets 1 and 2 showed mean AA losses of 3% and 5%, respectively, while the reference diet had a mean AA leaching of 6%. The AA that had the highest leaching rates were lysine (21%), methionine (15%), and histidine (12%). The ADC of dry matter was higher for poultry meals 1 (70%) and 2 (73%), followed by pork meal (69%), feather meals (61%), and blood meal (57%). The digestibility of CP was higher for poultry meals (78–80%), followed by pork meal (76%), and blood meal and feather meals (65–67%). The digestibility of CP in the reference diet (83%) was higher than that observed for all the animal by-product meals except the poultry meals. The ADC of the sum of AA adjusted for nutrient leaching fluctuated from 65% for blood meal to 80% for poultry meals.

Disturbance in hemoglobin metabolism and in vivo antimalarial activity of azole antimycotics

Plasmodium parasites degrade host hemoglobin to obtain free amino acids, essential for protein synthesis. During this event, free toxic heme moieties crystallize spontaneously to produce a non-toxic pigment called hemozoin or ß-hematin. In this context, a group of azole antimycotics, clotrimazole (CTZ), ketoconazole (KTZ) and fluconazole (FCZ), were investigated for their abilities to inhibit ß-hematin synthesis (IßHS) and hemoglobin proteolysis (IHbP) in vitro. The ß-hematin synthesis was recorded by spectrophotometry at 405 nm and the hemoglobin proteolysis was determined by SDS-PAGE 12.5%, followed by densitometric analysis. Compounds were also assayed in vivo in a malaria murine model. CTZ and KTZ exhibited the maximal effects inhibiting both biochemical events, showing inhibition of β-hematin synthesis (IC50 values of 12.4 ± 0.9 µM and 14.4 ± 1.4 µM respectively) and inhibition of hemoglobin proteolysis (80.1 ± 2.0% and 55.3 ± 3.6%, respectively). There is a broad correlation to the in vivo results, especially CTZ, which reduced the parasitemia (%P) of infected-mice at 4th day post-infection significantly compared to non-treated controls (12.4 ± 3.0% compared to 26.6 ± 3.7%, p = 0.014) and prolonged the survival days post-infection. The results indicated that the inhibition of the hemoglobin metabolism by the azole antimycotics could be responsible for their antimalarial effect.

Dietas vegetarianas e desempenho esportivo

As evidências atuais apontam benefícios da dieta vegetariana para a saúde humana. Contudo, a partir da adoção de práticas vegetarianas mais restritivas, confirmam-se os riscos à saúde. As dietas vegetarianas são caracterizadas pelo elevado consumo de carboidratos, fibras, magnésio, potássio, folato e antioxidantes, podendo apresentar deficiências em aminoácidos e ácidos graxos essenciais, cálcio, zinco, ferro e cobalamina. Pesquisas experimentais em humanos indicam que vegetarianos e não-vegetarianos apresentam capacidade aeróbica semelhante. em relação ao desempenho em atividades de força e potência muscular, as pesquisas são escassas, mas as existentes não apontam diferenças significativas. Situações de risco cardiovascular têm sido confirmadas, devido ao provável quadro de hiperhomocisteinemia, em decorrência da baixa ingestão de cobalamina. As dietas vegetarianas são isentas de creatina, o que resulta em estoques musculares mais baixos nessa população. Possivelmente ocorrem alterações hormonais e metabólicas em resposta às dietas vegetarianas, como baixos níveis de testosterona e androstenediona. A função imune parece não ser prejudicada. Dessa forma, a prática de dietas vegetarianas apresenta-se compatível com a prática esportiva cotidiana, desde que bem planejada para evitar deficiências nutricionais.

Unveiling the molecular mechanism of BRCA2-RAD51 interaction to tackle cancer onset

Different kinds of lesions can occur to DNA, and among them, one of the most dangerous is the double strand breaks (DSBs). Actually, DSBs can result in mutations, chromosome translocation or deletion. For this kind of lesions, depending on cell cycle phase as well as DNA-end resection, cells have developed specific repair pathways. Among these the error-free homologous recombination (HR) plays a crucial role. HR takes place during S/G2 phases, since the sister chromatids can be used as homologous templates. In this process, hRAD51 and BRCA2 are key players. hRAD51 is a recombinase of 339 amino-acids highly conserved through evolution which displays an intrinsic tendency to form oligomeric structures. BRCA2 is a very large protein of 3418 amino-acids, essential for the recruitment and accumulation of hRAD51 in the nucleus repairing-foci. BRCA2 interacts with hRAD51 through eight, so-called, BRC repeats, composed of 35-40 amino-acids. Mutations within this region have been linked to an increased risk of ovarian cancer development. In particular, several reports highlighted that missense mutations within one BRC repeat can hamper BRCA2 activity. Considering the close homology between the BRC repeats, it is striking how these mutations cannot be counterbalanced by the other non-mutated repeats preserving the function and the interactions of BRCA2 with hRAD51. To date the only interaction that has been structurally elucidated, is the one taking place amid the fourth BRC repeat and hRAD51. Only very little biophysical information is available on the interaction of the other BRC repeats with hRAD51. This thesis aims at elucidating the mechanism of hRAD51-BRCA2 interaction, by means of biophysical and structural approaches.

Effect of prolonged intravenous glucose and essential amino acid infusion on nitrogen balance, muscle protein degradation and ubiquitin-conjugating enzyme gene expression in calves

Background: Intravenous infusions of glucose and amino acids increase both nitrogen balance and muscle accretion. We hypothesised that co-infusion of glucose ( to stimulate insulin) and essential amino acids (EAA) would act additively to improve nitrogen balance by decreasing muscle protein degradation in association with alterations in muscle expression of components of the ubiquitin-proteasome proteolytic pathway. Methods: We examined the effect of a 5 day intravenous infusions of saline, glucose, EAA and glucose + EAA, on urinary nitrogen excretion and muscle protein degradation. We carried out the study in 6 restrained calves since ruminants offer the advantage that muscle protein degradation can be assessed by excretion of 3 methyl-histidine and multiple muscle biopsies can be taken from the same animal. On the final day of infusion blood samples were taken for hormone and metabolite measurement and muscle biopsies for expression of ubiquitin, the 14-kDa E2 ubiquitin conjugating enzyme, and proteasome sub-units C2 and C8. Results: On day 5 of glucose infusion, plasma glucose, insulin and IGF-1 concentrations were increased while urea nitrogen excretion and myofibrillar protein degradation was decreased. Co-infusion of glucose + EAA prevented the loss of urinary nitrogen observed with EAA infusions alone and enhanced the increase in plasma IGF-1 concentration but there was no synergistic effect of glucose + EAA on the decrease in myofibrillar protein degradation. Muscle mRNA expression of the ubiquitin conjugating enzyme, 14-kDa E2 and proteasome sub-unit C2 were significantly decreased, after glucose but not amino acid infusions, and there was no further response to the combined infusions of glucose + EAA. Conclusion: Prolonged glucose infusion decreases myofibrillar protein degradation, prevents the excretion of infused EAA, and acts additively with EAA to increase plasma IGF-1 and improve net nitrogen balance. There was no evidence of synergistic effects between glucose + EAA infusion on muscle protein degradation or expression of components of the ubiquitin-proteasome proteolytic pathway.

Amino-terminal protein processing in Saccharomyces cerevisiae is an essential function that requires two distinct methionine aminopeptidases.

We previously characterized a methionine aminopeptidase (EC 3.4.11.18; Met-AP1; also called peptidase M) in Saccharomyces cerevisiae, which differs from its prokaryotic homologues in that it (i) contains an N-terminal zinc-finger domain and (ii) does not produce lethality when disrupted, although it does slow growth dramatically; it is encoded by a gene called MAP1. Here we describe a second methionine aminopeptidase (Met-AP2) in S. cerevisiae, encoded by MAP2, which was cloned as a suppressor of the slow-growth phenotype of the map1 null strain. The DNA sequence of MAP2 encodes a protein of 421 amino acids that shows 22% identity with the sequence of yeast Met-AP1. Surprisingly, comparison with sequences in the GenBank data base showed that the product of MAP2 has even greater homology (55% identity) with rat p67, which was characterized as an initiation factor 2-associated protein but not yet shown to have Met-AP activity. Transformants of map1 null cells expressing MAP2 in a high-copy-number plasmid contained 3- to 12-fold increases in Met-AP activity on different peptide substrates. The epitope-tagged suppressor gene product was purified by immunoaffinity chromatography and shown to contain Met-AP activity. To evaluate the physiological significance of Met-AP2, the MAP2 gene was deleted from wild-type and map1 null yeast strains. The map2 null strain, like the map1 null strain, is viable but with a slower growth rate. The map1, map2 double-null strains are nonviable. Thus, removal of N-terminal methionine is an essential function in yeast, as in prokaryotes, but yeast require two methionine aminopeptidases to provide the essential function which can only be partially provided by Met-AP1 or Met-AP2 alone.