Inhibition of the angiotensin-converting enzyme by grape seed and skin proanthocyanidins extracted from Vitis vinífera L. cv. País

The influence of two extracts of grape skin and seeds from Vitis vinífera L. cv. País (Chilean black grapes), rich in proanthocyanidins (PAs), was evaluated on the inhibition of the angiotensin I-converting enzyme (ACE), and the inhibition was related to the type and number of subunits of the polymeric PAs chain. Size exclusion chromatography was used to purify the extract and its characterization was made by acid catalysis depolymerization followed by HPLC. ACE activity was measured by quantitative HPLC, measuring the hyppuric acid (HA) produced from the hydrolysis of hippuryl-l-histidyl-l-leucine (HHL) by ACE. Structural compositions differed significantly between both extracts: the skin extracts do not exhibit epicatechin (EC) and epicatechin gallate (ECG), and the seed extracts did not present epigallocatechin (EGC). Skin extracts have a higher mean degree of polymerization (mDP) than seed extracts and a higher inhibition power (IC₅₀ = 0.14 ± 0.03 μM and IC₅₀ = 0.480 ± 0.03 μmol/L), respectively. The catechin (IC₅₀ = 1495 ± 90 μmol/L) and epicatechin (IC₅₀ = 1772 ± 121 μmol/L) monomers exerted lower inhibition than the either grape extract. The structural differences between grape skin and seed PAs could influence the ACE inhibition capacity. The larger inhibitory power of skin extract was associated to greater OH availability, higher mDP and the presence of EGC.     

Freeze-thaw stability of oil-in-water emulsions prepared with native and thermally-denatured soybean isolates

Freeze-thaw stability of oil-in-water emulsions prepared with native or thermally-denatured soy isolates (NSI and DSI, respectively) as the sole emulsifier and sunflower oil (? = 0.25) has been examined at various protein concentrations (0.5, 1.0 and 2.0% w/v), comparatively with sodium caseinate (SC). The freeze-thaw stability was assessed by measurements of particle size, oiling off and gravitational separation after isothermal storage at −20 °C for 24 h and further thawing. The oil phase remained in liquid state and the amount of ice formed was similar (>97%) whatever the sample type and protein concentration. At 0.5%, NSI and DSI emulsions where highly unstable, exhibiting a coagulated cream layer with appreciable oiling off (>25%), whereas those prepared with SC were more stable, due to their initial lower flocculation degree (FD %) and particle size. For all emulsions, the increase of protein concentration (0.5–2.0% w/v) improves the freeze-thaw stability as a consequence of a decrease of initial FD %. At 2.0%, where is enough protein to cover the interface, a lower coalescence stability of NSI emulsion respect to those prepared with NSI was observed after freeze-thawing. This result can be attributed to the high tendency to aggregation of native soy globulins at subzero temperatures. Notwithstanding this, unlike the SC emulsions, the formation of new flocs in soy isolates-stabilized emulsions during freeze-thawing cannot be totally controlled.     

Beam waveguide for ECRH at TJ-II

In this paper we present the main parameters of the transmission line system for Electron Cyclotron Resonance Heating (ECRH) for the TJ-II experiment at theAsociación Euratom Ciemat para Fusión in Madrid. This heating system is based on two quasioptical transmission lines carrying 400 kW and 0.5 sec. of pulse length each line and operating at the frequency of 53.2 GHz. The principal parameters of the designed mirrors and those of the guided beams are given in this paper. The first transmission line has already been built at the Ciemat workshop, the second one is under construction.     

Haemophilus somnus immunoglobulin binding proteins and surface fibrils

The high-molecular-weight (HMW) immunoglobulin binding proteins (IgBPs) of Haemophilus somnus and a 76-kDa surface protein (p76) are found in serum-resistant virulent strains but not in several serum-sensitive strains from asymptomatic carriers. For the first time, p76 was shown to be an IgBP also. This was done by competitive inhibition studies with affinity-purified antidinitrophenol (anti-DNP) and DNP to ensure that binding was not antigen specific. The HMW IgBPs, but not the p76 IgBP, were partially purified from concentrated culture supernatant in detergent by fluid-phase liquid chromatography with a gel filtration column. Membrane extraction studies showed that p76 predominated in the Sarkosyl-soluble fraction of the bacterial cell pellet. Since integral outer membrane (OM) proteins are Sarkosyl insoluble, this is consistent with our previous finding that implicated p76 as a peripheral OM protein. The HMW IgBPs were found predominantly in the Sarkosyl-soluble fraction of the culture supernatant. This suggests that they were not integral membrane proteins and that their presence in the supernatant was not due to OM blebbing. We then showed that two IgBP-positive serum-resistant virulent strains have a surface fibrillar network but that two IgBP-negative serum-sensitive H. somnus strains from asymptomatic preputial carriers do not. Fibrils on the surfaces of IgBP+ strains bound gold-labelled bovine immunoglobulin G2 (IgG2) anti-DNP, indicating that these fibrils have IgG2 binding activity. Therefore, this study shows that H. somnus has two IgBPs, including a peripheral membrane protein and a fibrillar surface network.     

Nonphosphorylated peptide ligands for the Grb2 Src homology 2 domain

Critical intracellular signals in normal and malignant cells are transmitted by the adaptor protein Grb2 by means of its Src homology 2 (SH2) domain, which binds to phosphotyrosyl (pTyr) residues generated by the activation of tyrosine kinases. To understand this important control point and to design inhibitors, previous investigations have focused on the molecular mechanisms by which the Grb2 SH2 domain selectively binds pTyr containing peptides. In the current study, we demonstrate that the Grb2 SH2 domain can also bind in a pTyr independent manner. Using phage display, an 11-amino acid cyclic peptide, G1, has been identified that binds to the Grb2 SH2 domain but not the src SH2 domain. Synthetic G1 peptide blocks Grb2 SH2 domain association (IC50 10-25 microM) with a 9-amino acid pTyr-containing peptide derived from the SHC protein (pTyr317). These data and amino acid substitution analysis indicate that G1 interacts in the phosphopeptide binding site. G1 peptide requires a YXN sequence similar to that found in natural pTyr-containing ligands, and phosphorylation of the tyrosine increases G1 inhibitory activity. G1 also requires an internal disulfide bond to maintain the active binding conformation. Since the G1 peptide does not contain pTyr, it defines a new type of SH2 domain binding motif that may advance the design of Grb2 antagonists.     

Control of mutation frequency by bacteriophage T4 DNA polymerase. II. Accuracy of nucleotide selection by the L88 mutator, CB120 antimutator, and wild type phage T4 DNA polymerases

The ts CB1200 (antimutator) mutation in bacteriophage T4 DNA polymerase increases the accuracy of DNA replication since it results in a decrease in the frequency of mutations in other phage genes. The CB120 polymerases differs from the wild type enzyme in the slow rate at which it copies templates where primer extension requries displacement of polynucleotides base-paired to the template strand, even in the presence of the T4 DNA unwinding protein (gene 32-protein). The ratio of nucleotides turned over (DNA-dependent conversion of deoxynucleoside triphosphate to deoxynucleoside monophosphate) to nucleotides stably incorporated into product is 10 to 100 times higher with the mutant than wild type enzyme, depending on the DNA used as the template. This high turnover rate may increase the efficiency of removal of noncomplementary nucleotides by the antimutator enzyme and is in agreement with the findings of Muzyczka et al, (Muzyczka, N., Poland, R. L., and Bessman, M. J. (1972) J. Biol, Cehm. 247, 7116-7122) with the L141 and L42 antimutator T4 DNA polymerases. Since the 3'- to 5'-exonuclease activity of the CB120 mutant polymerase is not higher than that of the wild type enzyme, it is suggested that the high turnover rate may result from increased opportunity to remove newly incorporated nucleotides due to the slow rate at which the mutant enzyme moves to the next template nucleotide. In the accompanying paper we show that the CB120 antimutator polymerase also initially selects incorrect nucleotides for incorporation less frequently than the wild type enzyme. Thus this antimutator polymerase appears to have both greater accuracy in nucleotide selection and an enhanced ability to remove incorrect nucleotides.     

Altered efficacy and selectivity of tyrosine kinase inhibitors of the activated states of protein tyrosine kinases

Listeria monocytogenes is a pathogenic bacterium which has been implicated in several foodborne illnesses. This microorganism grows into biofilms attached to the surfaces in food-processing plants, increasing its resistance to antimicrobial agents. The present work was realized to investigate the attachment of L. monocytogenes isolates to glass surfaces and to find a decontamination procedure to remove these bacteria in biofilms. Three-day biofilms were prepared by growing L. monocytogenes isolates from food plant environments on glass surfaces. Sixteen decontamination treatments at different pHs, temperatures, and times of exposure were tested against L. monocytogenes biofilms. The most efficient treatments were those applied at 63 degrees C. Combinations of decontamination treatments applied at 55 degrees C for 30 min provided different results according to the other factors used. In general, L. monocytogenes biofilms were found to be not very susceptible to high osmolarity (10.5% NaCl), and the interaction of sodium chloride and acid did not seem to have important effects in inactivating these bacteria (from a 1.3-to a 1.9-log-CFU/cm2 reduction). The combination of NaOH (pH 10.5; 100 mM) and acetic acid (pH 5.4; 76.7 mM) applied sequentially at 55 degrees C for even 5 min was shown to be the most effective treatment to remove L. monocytogenes from biofilms (at least a 4.5-to 5.0-log-CFU/cm2 decline).     

Odor-related bulbar EEG spatial pattern analysis during appetitive conditioning in rabbits.

Five mildly thirsty male New Zealand rabbits were classically conditioned by reinforcement with water to give a discriminative licking response to the presentation of odors. The jaw-movement component of the licking conditioned response (CR) was elicited only by the reinforced odor; an increase in the relative frequency of sniffing occurred to both reinforced and nonreinforced odors. Oscillatory EEG bursts of high-frequency (40–80 Hz) potentials were recorded epidurally from the lateral olfactory bulb with 64-electrode arrays chronically implanted. Emphasis was on comparing bursts during odor presentation with bursts preceding odor arrival on each trial. A "detection" burst was characterized as occurring immediately after odor arrival and before the sniff response. "Discrimination" bursts occurred during the sniffing CR and before the jaw-movement CR onset. Significant air–odor burst differences (together with sniffing) occurred through up to 6 sessions for both reinforced and nonreinforced odors for discrimination bursts but not for detection bursts. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)