Check out our New Publishers' Select for Free Articles

Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.34, #2)

Structural properties of proteins specific to the myelin sheath by P. Kursula (pp. 175-185).

The myelin sheath is an insulating membrane layer surrounding myelinated axons in vertebrates, which is formed when the plasma membrane of an oligodendrocyte or a Schwann cell wraps itself around the axon. A large fraction of the total protein in this membrane layer is comprised of only a small number of individual proteins, which have certain intriguing structural properties. The myelin proteins are implicated in a number of neurological diseases, including, for example, autoimmune diseases and peripheral neuropathies. In this review, the structural properties of a number of myelin-specific proteins are described.

Keywords: Keywords: Myelin – Membrane protein – Unstructured protein – Posttranslational modification – Protein domain – Protein structure

S-adenosylmethionine and its products by M. A. Grillo; S. Colombatto (pp. 187-193).

S-adenosylmethionine is involved in many processes, mainly methylation, polyamine synthesis and radical-based catalysis. It is synthesised through the catalysis of differently regulated enzyme forms. When it is used, the compounds formed are reutilized in different ways: in case of methylation, its end product is homocysteine, which can be remethylated to methionine, give rise to cysteine in the so-called transsulphuration pathway, or be released; in the case of polyamine synthesis, the methylthioadenosine formed is cleaved and gives rise to compounds which can be reutilized; during radical-based catalysis, 5-deoxyadenosine is formed and this, too, is cleaved and reutilized.

Keywords: Keywords: Homocysteine – Methylthioadenosine – 5-Deoxyadenosine

DNA repair Ku proteins in gastric cancer cells and pancreatic acinar cells by H. Kim (pp. 195-202).

The DNA repair protein Ku acts as a heterodimer of Ku70 and Ku80 that binds to the DNA ends, nicks, or single-to-double-strand transition. It has a crucial role for DNA double-strand-break repair. Either Ku70 or Ku80 itself may have a unique function that is independent of the other Ku subunit. In this review, the role of Ku on cell proliferation and apoptosis will be discussed. Ku acts as a regulator of transcription by interacting with the recombination signal binding protein Jκ and the NF-κB p50 homodimer to up-regulate p50 expression, which may regulate the proliferation of gastric cancer cells. Both Ku70 and Ku80 expressions are mediated by constitutively activated NF-κB and constitutively expressed cyclooxygenase-2 in gastric cancer cells, which may be related to gastric cell proliferation and carcinogenesis. In addition, nuclear loss of Ku may underlie the mechanism of apoptosis in pancreatic acinar cells after oxidative stress.

Keywords: Keywords: DNA repair Ku protein – NF-κB – Cylooxygenase-2 – Apoptosis – Gastric cancer cells – Pancreatic acinar cells

Effects of active and passive hyperthermia on heat shock protein 70 (HSP70) by R. Lovell; L. Madden; L. R. McNaughton; S. Carroll (pp. 203-211).

The purpose of this study was to delineate the effects of hyperthermia and physical exercise on the heat shock protein 70 (HSP70) response in circulating peripheral blood mononuclear cells (PBMCs). Six healthy, young (age: 24 ± 3 yrs), moderately trained males (VO_2max: 48.9 ± 2.7 ml · kg · min⁻¹) undertook two experimental trials in a randomised fashion in which the core temperature (T _c) was increased and then maintained at 39 °C during a 90 min bout by either active (AH) or passive (PH) means. AH involved subjects cycling at 90% of their lactate threshold in attire designed to impede heat loss mechanisms. In the PH trial, subjects were immersed up to the neck in a hot bath (40.2 ± 0.4 °C), once the critical T _c was achieved, intermittent cycling and water immersions were prescribed for the AH and PH conditions, respectively, to maintain the T _c at 39 °C. HSP70 was measured intracellularly pre, post and 4 h after trials, from circulating PBMCs using an ELISA technique. T _c reached 39 °C quicker in PH than during AH trials (PH: 21 ± 4 min vs. AH: 39 ± 6 min; P < 0.01), thereafter T _c was maintained around 39 °C (PH: 39.1 ± 0.2 °C; AH: 38.8 ± 0.3 °C; P > 0.05). AH induced a marked leukocytosis in all sub-sets (P < 0.05). PH generated significant monocytosis and granulocytosis (P < 0.05), without changes in lymphocyte counts (P > 0.05). There were no significant increases in intracellular HSP70 at 0 h (AH: Δ − 21.1 ± 44.8; PH: Δ + 12.5 ± 32.4 ng/mg TP/10³/µl PBMCs; P > 0.05) and 4 h (AH: Δ − 30.0 ± 40.1; PH: Δ + 36.3 ± 70.4 ng/mg TP/10³/µl PBMCs; P > 0.05) post active and passive heating. Peak HSP70 expressed as a fold-change from rest was also not increased by AH (1.1 ± 0.9; P > 0.05) or PH (3.2 ± 4.8; P > 0.05). There were no significant differences between the AH and PH trials at any time-point, and the HSP70 response appeared to be individual specific. These results did not allow us to delineate the effects of hyperthermia and other exercise associated stressors on the heat shock response and therefore further work is warranted.

Keywords: Keywords: Exercise – Leukocytes – Temperature – Heat – Stress proteins

Regulation of aspartate-derived amino acid homeostasis in potato plants (Solanum tuberosum L.) by expression of E. coli homoserine kinase by J. Rinder; A. P. Casazza; R. Hoefgen; H. Hesse (pp. 213-222).

The availability of the carbon backbone O-phosphohomoserine (OPHS) is critical to methionine (met) and threonine (thr) synthesis. OPHS derives from homoserine and is formed by homoserine kinase (HSK). To clarify the function of HSK in cellular metabolism, the E. coli HSK ortholog thrB was expressed in potato plants targeting the EcHSK protein to chloroplasts and to the cytosol. Both approaches resulted in up to 11 times increased total HSK enzyme activity. Transgenic plants exhibited reduced homoserine levels while met and thr did not accumulate significantly. However, the precursor cysteine and upstream intermediates of met such as cystathionine and homocysteine did indicating an accelerated carbon flow towards the end products. Coincidently, plants with elevated cytosolic levels of EcHSK exhibited a reduction in transcript levels of the endogenous HSK, as well as of threonine synthase (TS), cystathionine β-lyase (CbL), and met synthase (MS). In all plants, cystathionine γ-synthase (CgS) expression remained relatively unchanged from wild type levels, while S-adenosylmethionine synthetase (SAMS) expression increased. Feeding studies with externally supplied homoserine fostered the synthesis of met and thr but the regulation of synthesis of both amino acids retained the wild type regulation pattern. The results indicate that excess of plastidial localised HSK activity does not influence the de novo synthesis of met and thr. However, expression of HSK in the cytosol resulted in the down-regulation of gene expression of pathway genes probably mediated via OPHS. We integrated these data in a novel working model describing the regulatory mechanism of met and thr homeostasis.

Keywords: Keywords: Aspartate family – Homoserine kinase – Methionine – Threonine – Potato

In silico analysis of arginine catabolism as a source of nitric oxide or polyamines in endothelial cells by R. Montañez; C. Rodríguez-Caso; F. Sánchez-Jiménez; M. Á. Medina (pp. 223-229).

We use a modeling and simulation approach to carry out an in silico analysis of the metabolic pathways involving arginine as a precursor of nitric oxide or polyamines in aorta endothelial cells. Our model predicts conditions of physiological steady state, as well as the response of the system to changes in the control parameter, external arginine concentration. Metabolic flux control analysis allowed us to predict the values of flux control coefficients for all the transporters and enzymes included in the model. This analysis fulfills the flux control coefficient summation theorem and shows that both the low affinity transporter and arginase share the control of the fluxes through these metabolic pathways.

Keywords: Keywords: Arginine – Nitric oxide – Ornithine – Polyamines – Metabolic control analysis

N-acetyl-L-cysteine as a source of sulfane sulfur in astrocytoma and astrocyte cultures: correlations with cell proliferation by H. Jurkowska; M. Wróbel (pp. 231-237).

N-acetyl-L-cysteine (NAC), a precursor of L-cysteine, not only elevates the level of glutathione in both astrocytoma and astrocyte cultures, but also affects the cellular level of sulfane sulfur. Astrocytoma cells were investigated using the stable U373 human cell line. In the U373 cells, N-acetyl-L-cysteine, depending on the concentration in the culture medium and culture duration, either elevated or diminished the level of sulfane sulfur, and this was respectively accompanied by decreased or increased cellular proliferation. In murine astrocytes, in turn, NAC was capable of lowering the level of sulfane sulfur and in this way decreased cellular proliferation. It seems that normal (astrocyte) and transformed (astrocytoma) cells differed in their reaction to NAC in the culture medium. The effect of N-acetyl-L-cysteine on astrocytoma cells was advantageous in that it inhibited their proliferation through the elevation of the level of sulfane sulfur.

Keywords: Keywords: Astrocytes – U373 cells – N-acetyl-L-cysteine – 3-Mercaptopyruvate sulfurtransferase – Rhodanese – Sulfane sulfur

Cinnamomin: separation, crystallization and preliminary X-ray diffraction study by T. Wang; Y.-S. Zou; D.-W. Zhu; A. Azzi; W.-Y. Liu; S.-X. Lin (pp. 239-243).

Cinnamomin from Cinnamonum camphora seeds, a type II ribosome-inactivating protein that interferes with protein biosynthesis in mammalian cells, can induce the apoptosis of carcinoma cells and be used as an insecticide. A rapid and improved method has been developed for the extraction and purification of cinnamomin from camphora seed. Purification of cinnamomin is achieved with two successive steps of hydrophobic interaction chromatography carried out on a fast protein liquid chromatography (FPLC) system. Crystals suitable for X-ray diffraction analysis were obtained by vapor diffusion method. A complete data set at 2.8 Å resolution has been collected. Data indexation and refinement indicate that the crystal is orthorhombic with space group P2₁2₁2₁ and unit cell dimensions a = 52.39 Å, b = 126.33 Å, c = 161.45 Å. There are two molecules per asymmetric unit. Initial phasing by molecular replacement method yielded a solution, which will contribute to the structure determination. A molecular model will further the understanding of the mechanism of cinnamomin function. The latter will be combined with bio-informatics to facilitate the medical and other applications of cinnamomin.

Keywords: Keywords: Cinnamomin – Crystallization – FPLC – Hydrophobic interaction chromatography – Ribosome-inactivating protein – X-ray crystal structure

Effects of creatine supplementation on glucose tolerance and insulin sensitivity in sedentary healthy males undergoing aerobic training by B. Gualano; R. B. Novaes; G. G. Artioli; T. O. Freire; D. F. Coelho; F. B. Scagliusi; P. S. Rogeri; H. Roschel; C. Ugrinowitsch; A. H. Lancha Jr (pp. 245-250).

Recent findings have indicated that creatine supplementation may affect glucose metabolism. This study aimed to examine the effects of creatine supplementation, combined with aerobic training, on glucose tolerance in sedentary healthy male. Subjects (n = 22) were randomly divided in two groups and were allocated to receive treatment with either creatine (CT) (∼10 g · day over three months) or placebo (PT) (dextrose). Administration of treatments was double blind. Both groups underwent moderate aerobic training. An oral glucose tolerance test (OGTT) was performed and both fasting plasma insulin and the homeostasis model assessment (HOMA) index were assessed at the start, and after four, eight and twelve weeks. CT demonstrated significant decrease in OGTT area under the curve compared to PT (P = 0.034). There were no differences between groups or over time in fasting insulin or HOMA. The results suggest that creatine supplementation, combined with aerobic training, can improve glucose tolerance but does not affect insulin sensitivity, and may warrant further investigation with diabetic subjects.

Keywords: Keywords: Creatine – Glucose tolerance – Insulin sensitivity – Aerobic training

Impairment of the metastatic activity of melanoma cells by transglutaminase-catalyzed incorporation of polyamines into laminin and Matrigel by A. Lentini; B. Provenzano; M. Caraglia; A. Shevchenko; A. Abbruzzese; S. Beninati (pp. 251-256).

Previously published evidences highlighted the effect of transglutaminase (TG, EC 2.3.2.13) activation on the reduction of the in vitro adhesive and invasive behaviour of murine B16-F10 melanoma cells, as well as in vivo. Here, we investigated the influence of spermidine (SPD) incorporation by TG into basement membrane components i.e. laminin (LN) or Matrigel (MG), on the adhesion and invasion of B16-F10 melanoma cells by these TG/SPD-modified substrates. The adhesion assays showed that cell binding to the TG/SPD-modified LN was reduced by 30%, when compared to untreated LN, whereas the reduction obtained using TG/SPD-modified MG was 35%. Similarly, tumor cell invasion by the Boyden chamber system through TG/SPD modified LN or MG was respectively reduced by 45%, and by 69%. Evaluation of matrix metalloproteinase (gelatinases MMP-2 and MMP-9) activities by gel-zymography showed that MMP-2 activity was unaffected, while MMP-9 activity was reduced by about 32% using TG/SPD-modified substrate. These results strongly suggest that the observed antiinvasive effect of TG activation in the host may be ascribed to the covalent incorporation of polyamines, which led to the post-translational modification of some components of the cell basement membrane. This modification may interfere with the metastatic property of melanoma cells, affecting the proteolytic activity necessary for their migration and invasion activities.

Keywords: Keywords: Melanoma cells – Invasion – Transglutaminase – Polyamines

Which mechanisms are involved in taurine-dependent granulocytic immune response or amino- and α-keto acid homeostasis? by J. Mühling; K. A. Nickolaus; R. Matejec; T. W. Langefeld; H. Harbach; J. Engel; M. Wolff; K. Weismüller; M. Fuchs; I. D. Welters; M. Krüll; M. C. Heidt; G. Hempelmann (pp. 257-270).

We examined the effects of β-alanine (taurine analogue and taurine transport antagonist), taurine (regarding its role in neutrophil (PMN) immunonutrition) and taurine combined either with L-NAME (inhibitor of •NO-synthase), SNAP (•NO donor), DON (glutamine-analogue and inhibitor of glutamine-requiring enzymes), DFMO (inhibitor of ornithine-decarboxylase) and β-alanine on neutrophil amino- and α-keto acid profiles or important PMN immune functions in order to establish whether taurine transport-, nitric oxide-, glutamine- or ornithine-dependent mechanisms are involved in any of the taurine-induced effects. According to the present findings, the taurine-mediated effect appears to be based primarily on a modulation of important transmembraneous transport mechanisms and only secondarily on directly or indirectly induced modifications in intragranulocytic amino- and α-keto acid homoeostasis or metabolism. Although a direct relation to the parallel observed immunological modifications can only be presumed, these results show very clearly that compositional modifications in the free intragranulocytic amino- and α keto-acid pools coinciding with changes in intragranulocytic taurine levels are relevant metabolic determinants that can significantly influence the magnitude and quality of the granulocytic immune response.

Keywords: Keywords: Taurine – β-alanine – DON – L-NAME – SNAP – DFMO – Neutrophils (PMN) – Amino acids – α-keto acids – Immune function

Cadmium and heat response of the fungus Heliscus lugdunensis isolated from highly polluted and unpolluted areas by J. Miersch; K. Grancharov (pp. 271-277).

Induction of heat shock protein (Hsp) 70 and distinct metallothionein-like proteins (MTLPs) in response to Cd and heat treatment were studied in two strains of the aquatic hyphomycete Heliscus lugdunensis: Hl-H4, isolated from a heavy metal polluted site, and Hl-BB taken from an unpolluted area. Upon Cd-exposure, Hsp70 was actively synthesized in the strain Hl-H4, and to a much lower degree in the strain Hl-BB. The Hsp70-expression was time- and dose-dependent, reaching a maximum after 24 h incubation with 80 µM Cd. Upon heat-stress, a similar response was observed: a strong Hsp70-expression in Hl-H4, and only a marginal one in Hl-BB. The strains reacted to Cd-exposure by a specific, environmentally related induction of MTLPs, as shown by the highly sensitive bimane derivatisation method of SH-rich proteins. In Hl-H4, a strong expression of 11 kDa MTLP was registered, which followed strictly the induction pattern of Hsp70. This suggests interdependence of the induction mechanisms and roles of these stress proteins in metal resistance. On the contrary, in Hl-BB a weak expression of MTLP of about 20 kDa was observed, exhibiting completely different induction pattern. The results suggest that the specific induction of Hsp70 and/or distinct MTLPs in the range of 11 kDa in H. lugdunensis strain Hl-H4 are essential adaptive mechanisms to continuous heavy metal exposure.

Keywords: Keywords: Cadmium – Heat stress – Metallothioneins – Aquatic hyphomycetes – Heliscus lugdunensis strains

Nano-structured support materials, their characterisation and serum protein profiling through MALDI/TOF-MS by M. Najam-ul-Haq; M. Rainer; N. Heigl; Z. Szabo; R. Vallant; C. W. Huck; H. Engelhardt; K.-D. Bischoff; G. K. Bonn (pp. 279-286).

In the bioanalytical era, novel nano-materials for the selective extraction, pre-concentration and purification of biomolecules prior to analysis are vital. Their application as affinity binding in this regard is needed to be authentic. We report here the comparative application of derivatised materials and surfaces on the basis of nano-crystalline diamond, carbon nanotubes and fullerenes for the analysis of marker peptides and proteins by material enhanced laser desorption ionisation mass spectrometry MELDI-MS. In this particular work, the emphasis is placed on the derivatization, termed as immobilised metal affinity chromatography (IMAC), with three different support materials, to show the effectiveness of MELDI technique. For the physicochemical characterisation of the phases, near infrared reflectance spectroscopy (NIRS) is used, which is a well-established method within the analytical chemistry, covering a wide range of applications. NIRS enables differentiation between silica materials and different fullerenes derivatives, in a 3-dimensional factor-plot, depending on their derivatizations and physical characteristics. The method offers a physicochemical quantitative description in the nano-scale level of particle size, specific surface area, pore diameter, pore porosity, pore volume and total porosity with high linearity and improved precision. The measurement takes only a few seconds while high sample throughput is guaranteed.

Keywords: Keywords: Nano materials – Diamond – Nanotubes – Fullerenes – MELDI – Silica – NIRS

The influence of extrusion on loss and racemization of amino acids by J. Csapó; É. Varga-Visi; K. Lóki; Cs. Albert; Sz. Salamon (pp. 287-292).

The influence of the operation conditions (temperature and residence time) of a thermic treatment on the total amount (free and protein-bound) of amino acid enantiomers of dry fullfat soya was investigated. Total amino acid content was determined using conventional ion-exchange amino acid analysis of total hydrolysates and chiral amino acid analysis was performed by HPLC after precolumn derivatization with o-phthaldialdehyde and 1-thio-β-D-glucose tetraacetate. Contrary to corn that was investigated previously, notable racemization was detected even at lower temperatures. At 140 °C the ratio of the D-enantiomer was 0.87% for glutamic acid, 2.81% for serine, and 1.92% for phenylalanine; at 220 °C the ratios of the D-enantiomer of the above amino acids were 1.43, 4.61, and 4.68%, respectively. The concentration of several L-amino acids decreased. At 220 °C there was 10% less L-glutamic acid, 17% less L-serine, 5% less L-phenylalanine, 6.6% less L-aspartic, acid and 21% less L-lysine than in the control; their loss can be assigned to different degrees of L – D conversion. While nearly complete transformation of L-phenylalanine can be attributed to racemization, the main cause of the loss of L-lysine is not racemization. The treatments in the same order of magnitude resulted in the formation of more D-amino acids and greater extent of racemization of amino acids in fullfat soya than that of maize.

Keywords: Keywords: Racemization – D-amino acid – Fullfat soybeans – Extrusion temperature – Residence time

The inhibitory effect of various indolyl amino acid derivatives on arginase activity in macrophages by A. Hrabák; T. Bajor; G. Mészáros (pp. 293-300).

Numerous indolyl amino acids and their derivatives inhibited arginase activity. The inhibition was found to be non-competitive, – at least partly – allosteric, and independent on manganese ions in the active site, and it cannot be explained by the dissociation of arginase homotrimers. Indole alone is weakly inhibitory; however, the presence of three-carbon side chains and their net charges is favorable for the inhibition. The binding of the inhibitory compounds caused only minor changes in the steric structure of arginase: a slight increase in α-helix content was detected by circular dichroism together with a decrease in parallel pleated sheet and β-turn sections. A slight alteration in the tertiary structure was also found using tryptophane fluorescence studies, but buried apolar side chains were not transposed to the protein surface. Computer studies that were performed did not provide additional structural information.

Keywords: Keywords: Arginase – Indolyl amino acid derivatives – Inhibitors – Minor steric alterations – Nitric oxide synthase

Bio-available amino acids and mineral nitrogen forms in soil of moderately mown and abandoned mountain meadows by P. Formánek; K. Rejšek; V. Vranová; M. V. Marek (pp. 301-306).

The abandonment of traditional mowing methods of mountain meadows in the Czech Republic at the end of the last century has resulted in secondary re-colonization of these areas. Altered accumulation of plant biomass resulted in a deceleration of N turnover. A mountain meadow may be regarded as a N-limited ecosystem in which plant nutrition is dependent on direct uptake of soil amino acids. The composition and distribution of ammonium ions, nitrate ions and the 16 bio-available proteinaceuous amino acids were investigated in the top 7 cm of the Ah horizon of a Gleyic Luvisol in a long-term moderately mown meadow and an eleven year old, abandoned or uncut meadow. Ammonium N has a dominant role in both ecosystems. The moderately mown meadow showed accelerated N-turnover and higher net ammonization. The plant community showed a dependence on this form. Plant utilization of nitrates and amino acids appeared to be negligible. The uncut or abandoned meadow showed net ammonization from May (start of the experiment) through August, after which plant N-uptake consisted only of amino acids due to microbial immobilization. The release of bio-available nitrogen from spring until the beginning of summer in the Ah horizon was too low to explain total plant N-uptake. Glutamic acid, arginine and aspartic acids had the highest concentrations of any of the amino acids analyzed.

Keywords: Keywords: Soil bio-available amino acids – Mountain meadows – Abandonment – Mowing – Mineral nitrogen forms

Quality and flavour stability of coffee substitute prepared by extrusion of wheat germ and chicory roots by H. H. M. Fadel; M. A. Abdel Mageed; S. N. Lotfy (pp. 307-314).

A mixture of roasted chicory roots and wheat germ (1:1 w/w) was subjected to extrusion processing for preparation of coffee substitute. Comparative studies concerning sensory characteristics and headspace volatiles were carried out between genuine coffee and a freshly prepared coffee substitute. The sensory evaluation revealed similarities between the two samples. The comparative odour profile analysis showed that the sweetish/caramel-like note scored higher in our coffee substitute sample than in real coffee, whereas the other odour quality attributes showed an opposite trend. The high quality of the fresh coffee substitute was correlated to the presence of volatiles that are responsible for the fresh coffee aroma, such as: 2-methylbutanal, 3-methylbutanal, 2-methylfuran and 2,3-butanedione in high concentration. Storage of coffee substitute samples revealed a noticeable decrease in concentration of the Strecker aldehydes and diketones and a remarkable increase in phenolic compounds, whereas pyrazine and furan derivatives showed no linear changes during storage. The ratio of 2,3-butanedione/2-methylfuran (B/M) was used as an indicator for aging of coffee substitute samples. The variation in this ratio (B/M) during storage for 6 months was consistent with that of the odour profile analysis.

Keywords: Keywords: Coffee substitute – Extrusion – Volatilies – Chicory roots – Wheat germ – Sensory evaluation

Free radical scavenging potential of L-proline: evidence from in vitro assays by S. Kaul; S. S. Sharma; I. K. Mehta (pp. 315-320).

An assessment of the potential of proline to scavenge free radicals was made in a couple of in vitro assay systems, namely graft co-polymerization and autooxidation of pyrogallol. Both these assays are essentially dependent upon free radical mechanisms. Graft co-polymerization involved a ceric (Ce⁴⁺) ion- or γ-radiation-induced grafting of methyl acrylate (MA) onto a cellulose backbone. The degree of grafting, measured gravimetrically, was taken as a measure of free radical generation. The γ-radiation-dependent grafting was far greater than that due to Ce⁴⁺ ions. Inclusion of proline in the assay, irrespective of the initiator used, led to suppression of grafting in a concentration-dependent manner indicating the ability of proline to scavenge free radicals. The γ-radiation-dependent grafting was also suppressed by hydroquinone and glutathione but not by ascorbate, glycine and spermine. In contrast to graft co-polymerization, proline did not inhibit the autooxidation of pyrogallol, a reaction involving superoxide radical generation. A subset of data constitutes an evidence for the ability of proline to scavenge free radicals in vitro. It is implied by extension that free proline, known to accumulate in plant tissues during abiotic stresses, would contribute to scavenging of surplus free radicals produced under a variety of abiotic stresses.

Keywords: Keywords: Cellulose – Free radicals – Graft co-polymerization – Methyl acrylate – Proline

Taurine increases mitochondrial buffering of calcium: role in neuroprotection by A. El Idrissi (pp. 321-328).

We have determined the role of mitochondria in the sequestration of calcium after stimulation of cerebellar granule cells with glutamate. In addition we have evaluated the neuroprotective role of taurine in excitotoxic cell death. Mitochondrial inhibitors were used to determine the calcium buffering capacity of mitochondria, as well as how taurine regulates the ability of mitochondria to buffer intracellular calcium during glutamate depolarization and excitotoxicity. We report here that pre-treatment of cerebellar granule cells with taurine (1 mM, 24 h) significantly counteracted glutamate excitotoxicity. The neuroprotective role of taurine was mediated through regulation of cytoplasmic free calcium ([Ca²⁺] i), and intra-mitochondrial calcium homeostasis, as determined by fluo-3 and ⁴⁵Ca²⁺-uptake. Furthermore, the overall mitochondrial function was increased in the presence of taurine, as assessed by rhodamine accumulation into mitochondria and total cellular ATP levels. We specifically tested the hypothesis that taurine reduces glutamate excitotoxicity through both the enhancement of mitochondrial function and the regulation of intracellular (cytoplasmic and intra-mitochondrial) calcium homeostasis. The role of taurine in modulating mitochondrial calcium homeostasis could be of particular importance under pathological conditions that are characterized by excessive calcium overloads. Taurine may serve as an endogenous neuroprotective molecule against brain insults.

Keywords: Keywords: Taurine – Excitotoxicity – Calcium homeostasis – Mitochondria

Reactivity and oxidative potential of fructose and glucose in enkephalin-sugar model systems by A. Jakas; Š. Horvat (pp. 329-332).

The reactions of Leu- and Met-enkephalin (Tyr-Gly-Gly-Phe-Leu/Met) with fructose resulted in the parallel formation of Heyns compounds (N-peptidyl-d-mannosamine and -d-glucosamine) and sugar-peptide generated imidazolidinone diastereomers. Glucose showed higher level of reactivity than fructose with respect to the extent of glycated product formation. The presence of fructose in the incubation mixtures makes Met residue more susceptible to oxidation than glucose.

Keywords: Keywords: Enkephalin – Fructose – Glucose – Glycation – Heyns – Imidazolidinone – Maillard

Synthesis of a versatile constrained analogue of dipeptide DG (Asp-Gly) by R. Galeazzi; E. Marcucci; G. Martelli; D. Natali; M. Orena; S. Rinaldi (pp. 333-336).

The synthesis of an orthogonally protected constrained analogue of dipeptide DG (Asp-Gly) is reported exploiting alkylation of a chiral lactam. The versatility of this analogue was proven by removal of t-Boc protecting group, followed by coupling under homogeneous conditions with t-Boc-Arg(Z₂)-Gly, to give a conformationally restricted analogue of RGDG tetrapeptide.

Keywords: Keywords: Amino acids – Mimetics – Lactams – Conformational restriction – Orthogonal protection

Sections

Personal tools

Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.34, #2)

Sections

Personal tools

Local resources

Amino Acids: The Forum for Amino Acid, Peptide and Protein Research (v.34, #2)