An acetylated N-terminus of adenovirus type 2 hexon protein

An acetylated N-terminus of adenovirus type 2 hexon protein was characterized using radioactively labeled protein and mass spectrometry. The labeled protein, obtained by synthesis in a medium containing ¹⁴C-acetate, was digested with proteolytic enzymes. A radioactive peptide, Acetyl-Ala-Thr-Pro-Ser, recovered in good yield, was the only N-terminal structure detected in the protein.     

An investigation of the mechanism of activation of tryptophan by tryptophanyl-tRNA synthetase from beef pancreas

Exposure of dark-grown Euglena to white or red light, but not blue light, produced a twofold increase in the specific activity of citrate synthase. A 400-fold purification of mitochondrial citrate synthase (subunit Mr = 44000) was achieved from cells of Euglena gracilis by affinity chromatography on ATP-activated agarose. Antisera, raised against the homogeneously pure enzyme, were used to demonstrate that the increase in citrate synthase activity on exposure of dark-grown cells to light resulted from an increase in citrate synthase protein. Anti-(citrate synthase) was used to detect precursor citrate synthase resulting from the translation of total polyadenylated RNA from Euglena in a cell-free rabbit reticulocyte lysate system. Citrate synthase mRNA was found to be present in cells at all stages of regreening. However, extraction and translation of polyadenylated RNA from free polysomes isolated from darkgrown and regreening cells demonstrated that appreciable translation of citrate synthase mRNA was only occurring in regreening cells.     

An acetylated galactoglucomannan from Picea abies L. Karst

A water-soluble galactoglucomannan composed of D-galactose, D-glucose, and D-mannose in 1:3:17 mole proportion has been isolated from the secondary cell walls of Picea abies L. Karst. About 33% of the polysaccharide units were substituted by acetyl groups. Structural studies of the polymer indicated a beta-(1-->4)-linked glucomannopyranosyl backbone with a low content of branch points at O-6 of mannosyl and glucosyl residues. A preference for mannosyl groups indicates the presence of a single D-galactosyl unit side-chain. About half of the mannose residues were O-acetylated at C-2 and C-3 in 1.7:1 mole proportion.     

An acetylated galactomannoglucan from the stems of Dendrobium nobile Lindl

A water-soluble polysaccharide DNP-W2 composed of glucose, mannose, and galactose in the molar ratio of 6.1:2.9:2.0 had been isolated from the stems of Dendrobium nobile. Its molecular weight was 1.8 × 10⁴ Da determined by HPGPC. Structural features of DNP-W2 were investigated by a combination of chemical and instrumental analysis, including FTIR, GC, GC-MS, periodate oxidation-Smith degradation, methylation analysis, partial acid hydrolysis, and NMR spectroscopy. The results showed that DNP-W2 is a 2-O-acetylgalactomannoglucan and has a backbone consisting of (1→4)-linked β-d-Glcp, (1→6)-linked β-d-Glcp, and (1→4)-linked β-d-Manp, with branches at O-6 of (1→4)-linked β-d-Glcp and β-d-Manp. The branches are composed of α-d-Galp. The acetyl groups are substituted at O-2 of (1→4)-linked Manp. Preliminary tests in vitro reveals that DNP-W2 can stimulate ConA- and LPS-induced T and B lymphocyte proliferation.     

An acetylated monoterpene and a sesquiterpene alcohol from Psiadia anchusifolia

Two compounds identified as 7,7-dimethyl-2-methylenebicyclo[3.1.1]heptan-6-ol acetate and 6,6,8,9-tetramethyltricyclo[3.3.3.0]undec-7-en-2-ol were isolated from the essential oil of the fresh leaves of Psiadia anchusifolia. Their structures were determined by extensive NMR studies (1H NMR, 13C NMR, DEPT, 1H-1H COSY, HSQC, HMBC) as well as by X-ray crystallographic analysis.     

Protein binding investigation by difference circular dichroism: Native and acetylated human serum albumins

A modified albumin was prepared by selective reaction of Lys₁₉₉ with acetyl salicylic acid. Protein binding investigation was carried out on native and modified proteins by difference circular dichroism (ΔCD). Acetylation of Lys₁₉₉ reduces significantly the effects of the interaction between drugs in the stereoselective HSA binding at specific binding areas. © 1995 Wiley-Liss, Inc.     

An investigation into the relevance of the pattern of temporal activation with respect to erector spinae muscle endurance

The aim of the present study was to evaluate the viability of a relationship between the temporal activation pattern of parts of the erector spinae muscle and endurance. Seven subjects performed intermittent isometric contractions [4 s at 7007o maximal voluntary contraction (MVC), 2 s rest] until exhaustion, during which the electromyographical (EMG) activity of the multifidus, iliocostalis thoracis and longissimus muscle segments was recorded. Endurance was defined as the time until exhaustion. Subjects were divided into a high and a low endurance group. The high endurance group showed significantly more variability of EMG amplitude over succeeding contractions. This group demonstrated significantly more alternations of EMG activity between parts of the muscle also. Variability of the EMG amplitude within the contractions did not differ between the groups, nor did MVC. The results indicated that alternating activity between different parts of the erector spinae muscle may function to postpone exhaustion of this muscle as a whole.     

Experimental investigation of the rheological activation of blood platelets

In order to define various aspects of platelet rheological activation, samples of whole blood and platelet-rich plasma (PRP) from the same donors were subjected for 5 min to shear rates increasing from 10 to 10000 sec-1 (shear stresses from 10(-2) to 30 Pa approximatively) in a Couette type viscometer. The following parameters were measured: erythrocyte hemolysis; lactic dehydrogenase activity; plasma B-Thromboglobulin (B-TG); adenine nucleotides, and platelet photometric aggregation. The experimental results reveal that: In whole blood, hemolysis only reached at maximum 2% of the total hemolysis. Plasma LDH activity increased regularly beyond 500 sec-1, in close correlation with B-TG plasma concentration. In contrast, ADP and ATP levels remained stable up to 1000 sec-1 then increased slowly. In PRP, the LDH, ADP and ATP levels remain practically stable up to shear rates around 5000 sec-1. In contrast, B-TG appeared to be released in plasma at shear rate values of 3000 sec-1 and its progression is only correlated with the other parameters, when the platelet lysis occurred. Finally, a rapid and complete inhibition of platelet aggregation to ADP was observed from 5000 sec-1.     

An NMR investigation of the changes in plasma membrane triglyceride and phospholipid precursors during the activation of T-lymphocytes.

Two-dimensional 1H-NMR spectroscopy was used to quantify the level of isotropically tumbling plasma membrane triglyceride and the intracellular concentrations of water-soluble phospholipid precursors during the activation of thymic T-lymphocytes. The concentration of "mobile" triglyceride in the plasma membrane was seen to increase 25-fold during 72 h of activation of murine thymic T-lymphocytes with ionomycin and phorbol myristate acetate. This is the first unequivocal demonstration of such a dramatic increase in mobile plasma membrane triglyceride during T-lymphocyte activation and leads to the suggestion that immune cell activation is associated with increased plasma membrane fluidity. The intracellular concentrations of choline- and ethanolamine-based phospholipid precursors were shown to increase during the early stages of T-lymphocyte activation and then remain at levels above those in resting cells. This may facilitate de novo phospholipid biosynthesis, which is presumably necessary since cell volume, and hence the plasma membrane surface area, was demonstrated to increase significantly during thymocyte activation.     

The use of acetylated factor X to prevent feedback activation of factor VIII during factor X activation: a tool for kinetic studies

The modification of human factor X by 2-sulfo-N-succinimidyl acetate was investigated and shown to produce a factor X species which, when activated, has no activity toward factor VIII. Acylation of factor X (0.9 microM) was carried out in the presence of 1 mM calcium at different reagent concentrations and pH values at 22 degrees C for time courses up to 1 h. Optimal modification was achieved using 0.3 mM reagent at pH 8.0 for 30 min. The modified zymogen, acetylated factor X, is activated at full rates by factor IXa/VIIIa and by the factor X-activating protein of Russell's viper venom. The activated product, acetylated Xa, has an enhanced amidolytic activity (110%) but has almost no detectable clotting activity (0.1%). More importantly, we have shown that acetylated Xa, in contrast to native Xa, does not activate factor VIII. This allows accurate quantitation of factor VIII activation without complications due to positive feedback reactions. We have demonstrated this in an examination of the activation of factor VIII by factor IXa.     

An investigation of large inhibitors binding to phosphoglycerate kinase and their effect on anion activation.

This study extends, to a series of larger anions, our earlier investigation of the interaction of the trypanocidal drug suramin and other small negatively charged molecules with yeast phosphoglycerate kinase. 1H-NMR structural studies of phosphoglycerate kinase in the presence of varying concentrations of these large molecules (designed to mimic, at one end, the anionic charge distribution in the substrate 3-phosphoglycerate, while possibly being able to interact across the cleft of the enzyme) including inositol 1,4,5-triphosphate, 4-amino-6-trichloroethenyl-1,3- benzenedisulphonamide, gallic acid and sulphasalazine are described. The anion activation and/or inhibition of the enzyme by these molecules are also reported. Evidence that binding to the general anion site in the 'basic patch' region of the protein may be responsible for either the activating or inhibiting effects, while binding at the hydrophobic (catalytic) site leads to inhibition only is presented. A reaction scheme which explains these observations is given.     

An investigation on the synthesis of borazine

Borazine is a promising precursor for boron nitride. A detailed investigation on the reaction of sodium borohydride and ammonium sulfate from 40 °C to 120 °C for synthesis of borazine was performed. The reaction was monitored by means of ¹¹B nuclear magnetic resonance (¹¹B NMR) and Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), mass spectroscopy (MS). The reaction produces mainly ammonia borane (AB), but not borazine at temperatures below 60 °C. Increases of temperature promote yield of borazine, which reaches the maximum around 110 °C. Whereas further increased temperature causes severe polymerization of borazine, and hence holds back yields of borazine.