MD — Simulation of Diffusion of Methane in Zeolites of Type LTA

Using molecular dynamical computer simulations (MD) the dynamics of kinetic processes in zeolites will be discussed on a molecular level. Small changes in lattice parameters can cause dramatical changes in the diffusion coefficient. The presence of cations Na⁺, Ca²⁺ also strongly influences the diffusion. Changes of the self-diffusivities will be discussed that appear if a vibrating lattice instead of a rigid one is used. Nonequilibrium simulations show the correlation between transport-diffusion and self-diffusion in zeolites.     

Which Copper is Paramagnetic in the Type 2/Type 3 Cluster of Laccase?

 Understanding the structure and function of the three copper atoms in the dioxygen reduction site of the blue oxidases such as laccase has been a long standing challenge. In the case of a widely studied derivative, known as type 2-depleted laccase, the removal of one copper from the cluster abolishes the EPR signal of the so-called type 2 copper. However, the present studies of isotopically enriched protein from Polyporus versicolor show that the readily replaceable copper is not active in the low-temperature EPR spectrum of fungal laccase or its difluoride adduct. The same is true for the difluoride adduct of the tree enzyme. Thus, in type 2-depleted laccase the pattern of antiferromagnetic coupling is quite different from that of the native protein or the difluoride adduct. Received: 5 October 1998 / Accepted: 13 January 1999     

The involvement of microRNAs in Type 2 diabetes

T2D (Type 2 diabetes mellitus) is a major health issue that has reached epidemic status worldwide. T2D is a progressive metabolic disorder characterized by reduced insulin sensitivity, insulin resistance and pancreatic β-cell dysfunction. Improper treatment of TD2 can lead to severe complications such as heart disease, stroke, kidney failure, blindness and nerve damage. The aetiology and molecular mechanisms of T2D are not fully understood, but compelling evidence points to a link between T2D, obesity, dyslipidaemia and insulin resistance. Although T2D seems to be strongly linked to environmental factors such as nutrition and lifestyle, studies have shown that genetic factors, such as polymorphisms associated with metabolic genes, imprinting, fetal programming and miRNA (microRNA) expression, could also contribute to the development of this disease. miRNAs are small 22-25-nt-long untranslated RNAs that negatively regulate the translation of mRNAs. miRNAs are involved in a large number of biological functions such as development, metabolism, immunity and diseases such as cancer, cardiovascular diseases and diabetes. The present review examines the various miRNAs that have been identified as being potentially involved in T2D, focusing on the insulin-sensitive organs: white adipose tissue, liver, skeletal muscle and the insulin-producing pancreatic β-cells.     

Overexpression of Cystathionine γ-Lyase Suppresses Detrimental Effects of Spinocerebellar Ataxia Type 3

Spinocerebellar ataxia type 3 (SCA3) is a polyglutamine (polyQ) disorder caused by a CAG repeat expansion in the ataxin-3 (ATXN3) gene resulting in toxic protein aggregation. Inflammation and oxidative stress are considered secondary factors contributing to the progression of this neurodegenerative disease. There is no cure that halts or reverses the progressive neurodegeneration of SCA3. Here we show that overexpression of cystathionine γ-lyase, a central enzyme in cysteine metabolism, is protective in a Drosophila model for SCA3. SCA3 flies show eye degeneration, increased oxidative stress, insoluble protein aggregates, reduced levels of protein persulfidation and increased activation of the innate immune response. Overexpression of Drosophila cystathionine γ-lyase restores protein persulfidation, decreases oxidative stress, dampens the immune response and improves SCA3-associated tissue degeneration. Levels of insoluble protein aggregates are not altered; therefore, the data implicate a modifying role of cystathionine γ-lyase in ameliorating the downstream consequence of protein aggregation leading to protection against SCA3-induced tissue degeneration. The cystathionine γ-lyase expression is decreased in affected brain tissue of SCA3 patients, suggesting that enhancers of cystathionine γ-lyase expression or activity are attractive candidates for future therapies.     

Resistance of Clostridium perfringens Type A Spores to γ-Radiation

The radiation resistance of the spores of a classical strain and of an atypical, heat-resistant strain of Clostridium perfringens was determined. Spores were produced in Ellner's and in a Trypticase broth medium. Approximately 10⁶ viable spores per milliliter were suspended in 0.06 m phosphate buffer and irradiated with γ rays from cobalt-60; the survivors were counted in Tryptone-yeast extract-agar by the Prickett-tube technique. Radiation D values for spores of the atypical strain in phosphate buffer and in cooked-meat broth were 0.23 and 0.30 Mrad, respectively, and the D value of the classical strain was 0.25 Mrad in phosphate buffer. Spores of the classical and atypical strains of C. perfringens type A are characterized by differences in heat resistance; yet, all strains tested demonstrated similar radiation resistance. Also, the spores were more resistant to ionizing radiation in cooked-meat broth than in phosphate buffer.     

Influence of Oil Type on Characteristics of β-Sitosterol and Stearic Acid Based Oleogel

Oleogels were prepared from extra virgin olive oil, corn oil, sunflower oil, and flaxseed oil with a mixture of β-sitosterol and stearic acid (Sit1:SA4, w/w) at concentrations of 15 and 20 g/100 g oil. The prepared oleogels were characterized by different methods to study the influence of oil type on the oleogel properties. The oil type influenced the colour and appearance of the oleogel. The flaxseed oil based oleogel showed lower oil loss and higher firmness than those of other oils based oleogels. The increase of gelator mixture from 15 to 20 g/100 g oil reduced the oil loss and improved the firmness of oleogel samples. The microscopy and small-angle x-ray scattering analyses showed different microstructures and crystallographic reflections for oleogels prepared from different oil types. Also, the oil type and concentration of gelator mixture influenced the melting and crystallization enthalpies of oleogel. Furthermore, different oils based oleogels showed varying values of viscosity, storage modulus (G’), and loss modulus (G”). Therefore, it can be concluded that the oil type and concentration of gelator influence the functional properties of oleogel and the flaxseed oil resulted in oleogel with good properties compared with other oils used in the study.     

Identification and Molecular Characterization of a Novel Type of α-galactosidase from Pyrococcus furiosus

An α-galactosidase gene from Pyrococcus furiosus was identified, cloned and functionally expressed in Escherichia coli. It is the first α-galactosidase from a hyperthermophilic archaeon described to date. The gene encodes a unique amino acid sequence compared to other α-galactosidases. Highest homology was found with α-amylases classified in family 57 of glycoside hydrolases. The 364 amino acid protein had a calculated mass of 41.6 kDa. The recombinant α-galactosidase specifically catalyzed the hydrolysis of para-nitrophenyl-α-galactopyranoside, and to some extent that of melibiose and raffinose. The enzyme proved to be an extremely thermo-active and thermostable α-galactosidase with a temperature optimum of 115°C and a half-life time of 15 hours at 100°C. The pH optimum is between 5.0 and 5.5. Sequence analysis showed four conserved carboxylic residues. Site-directed mutagenesis was applied to identify the potential catalytic residues. Glu117Ala showed decreased enzyme activity, which could be rescued by the addition of azide or formate. It is concluded that glutamate 117 is the catalytic nucleophile, whereas the acid/base catalyst remains to be identified.     

Effect of Sterol Type on Structure of Tubules in Sterol + γ-Oryzanol-Based Organogels

The mixture of γ-oryzanol with β-sitosterol forms a network of tubules in edible oil that may serve as an alternative to the network of small crystallites of triglycerides occurring in regular oil structuring. The present experiments demonstrate that the tubules vanish at the melting point of the gel. Moreover, a number of alternative sterols (e.g., ergosterol, stigmasterol, cholesterol, cholestanol) can replace sitosterol in the tubules. The tubule diameter varies between 6.7 and 8.0 nm, the wall thickness between 0.8 and 1.2 nm. The results are consistent with a previously proposed helical ribbon assembly mechanism.     

Meta-Analysis of Anti-Muscarinic Receptor Type 3 Antibodies for the Diagnosis of Sj?gren Syndrome

Purpose

To conduct a meta-analysis to evaluate the diagnostic value of anti-muscarinic receptor type 3 (M3R) antibodies in Sjögren syndrome (SS).

Methods

Two databases, PUBMED and the Cochrane Library, were systematically searched. Approximately 2,000 participants from several studies were included in this research. STATA 11.2 software and Meta-DiSc 1.4 was used to conduct the meta-analysis.

Results

Eleven studies were included in the meta-analysis. The pooled DOR was 13.00 (95% CI, 6.00–26.00). The sensitivity was 0.43 (95% CI, 0.28–0.58) and the specificity was 0.95 (95%CI, 0.91–0.97). The LR+ and LR- were 7.90 (95% CI, 4.70–13.40), 0.61 (95% CI, 0.46–0.79), respectively. The AUC was 0.89 (95% CI, 0.86–0.92).

Conclusion

The anti-M3R antibody had high specificity but relatively low sensitivity for the diagnosis of SS.     

Increasing incidence of Type 1 diabetes – role for genes?

Background  

The incidence of Type 1 diabetes (T1DM) is increasing fast in many populations. The reasons for this are not known, although an increase in the penetrance of the diabetes-associated alleles, through changes in the environment, might be the most plausible mechanism. After the introduction of insulin treatment in 1930s, an increase in the pool of genetically susceptible individuals has been suggested to contribute to the increase in the incidence of Type 1 diabetes.     

Effect of Pectin Type on Association and pH Stability of Whey Protein—Pectin Complexes

The purpose of this study was to investigate the influence of pectin type on complex formation between whey protein isolate (WPI) and high methoxy pectins with varying degrees of esterification (DE), and their pH stability. The biopolymer particles with protein-to-polysaccharide mass ratio set to 2:1 were formed at pH 3–7 by heating at 85 °C for 20 min. The particle size, electrical charge, turbidity and microstructure of the biopolymer complexes were evaluated. The optimal conditions for forming WPI-pectin complexes were at the initial pH of 4.5–4.75, just below the isoelectric point of the WPI, where complex formation occurs. At this pH range, the smallest biopolymer complexes (d?=?225–300 nm) could be created. Pectins with 50, 55, 62 and 70 % DE formed relatively small and monomodal complexes with WPI, except for pectin with 71 % DE, which showed major aggregation. The pH stability against aggregation was best with the biopolymer complexes assembled from pectins with 50 % DE (stable at pH 3.5–6.0) and with 62 % DE (stable at pH 3.0–6.0). The results suggest that pectins with varying DE can be used to form small particles and therefore can offer new possibilities in designing novel hierarchical structures and delivery systems.     

Apparent Involvement of a β1 Type Integrin in Coral Fertilization

Integrins are involved in a wide variety of cell adhesion processes, and have roles in gamete binding and fusion in mammals. Integrins have been also discovered in the scleractinian coral Acropora millepora (Cnidaria: Anthozoa). As a first step toward understanding the molecular basis of fertilization in corals, we examined the effect of polyclonal antisera raised against recombinant coral integrins on gamete interactions in A. millepora. Antiserum raised against integrin βcn1 dramatically decreased the binding of Acropora sperm to eggs and significantly decreased fertilization rates relative to preimmune serum and seawater controls. However, the antiserum against AmIntegrin α1 did not affect significantly either sperm–egg binding or fertilization. One possible explanation for this is that AmIntegrin α1 may preferentially mediate interactions with RGD-containing ligands, whereas mammalian α6 integrin (which is most directly implicated in gamete interactions) preferentially interacts with laminin-related ligands. Our results suggest that β1 type integrins are involved in the fertilization process in Acropora and that some functions of these molecules may have been conserved between corals and mammals. A. Iguchi and L. M. Márquez contributed equally to this work.     

The Pharmacology of the Benzodiazepine Site of the GABA-A Receptor is Dependent on the Type of γ-Subunit Present

Abstract

The pharmacology of native and recombinant GABA-A receptors containing either γ1, γ2 or γ3 subunits has been investigated. The pharmacology of native receptors has been investigated by immunoprecipitating receptors from solubilised preparations of rat brain with antisera specific for individual γ-subunits and analysing their radioligand binding characteristics. Receptors containing a γ1-subunit do not bind benzodiazepine radioligands with high affinity. Those containing either a γ2 or γ3 subunit bind [³H]flumazenil with high affinity. Some compounds compete for these binding sites with multiple affinities, reflecting the presence of populations of receptors containing several different types of α-subunit. Photoaffinity-labelling of GABA-A receptors from a cell line stably expressing GABA-A receptors of composition α₁β3γ2 followed by immunoprecipitation of individual subunits revealed that the α and γ but not the β-subunit could be irreversibly labelled by [³H]flunitrazepam.

The properties of recombinant receptors have been investigated in oocytes expressing γ1, γ2, or γ3 subunits in combination with an α and a β-subunit. Some compounds such as zolpidem, DMCM and flunitrazepam show selectivity for receptors containing different γ-subunits. Others such as CL 218,872 show no selectivity between receptors containing different γ-subunits but exhibit selectivity for receptors containing different α-subunits. These data taken together suggest that the benzodiazepine site of the GABA-A receptor is formed with contributions from both the α and γ-subunits.     

A Strategy for O-Glycoproteomics of Enveloped Viruses—the O-Glycoproteome of Herpes Simplex Virus Type 1

Glycosylation of viral envelope proteins is important for infectivity and interaction with host immunity, however, our current knowledge of the functions of glycosylation is largely limited to N-glycosylation because it is difficult to predict and identify site-specific O-glycosylation. Here, we present a novel proteome-wide discovery strategy for O-glycosylation sites on viral envelope proteins using herpes simplex virus type 1 (HSV-1) as a model. We identified 74 O-linked glycosylation sites on 8 out of the 12 HSV-1 envelope proteins. Two of the identified glycosites found in glycoprotein B were previously implicated in virus attachment to immune cells. We show that HSV-1 infection distorts the secretory pathway and that infected cells accumulate glycoproteins with truncated O-glycans, nonetheless retaining the ability to elongate most of the surface glycans. With the use of precise gene editing, we further demonstrate that elongated O-glycans are essential for HSV-1 in human HaCaT keratinocytes, where HSV-1 produced markedly lower viral titers in HaCaT with abrogated O-glycans compared to the isogenic counterpart with normal O-glycans. The roles of O-linked glycosylation for viral entry, formation, secretion, and immune recognition are poorly understood, and the O-glycoproteomics strategy presented here now opens for unbiased discovery on all enveloped viruses.     

Process of Infection with Bacteriophage φX174: XXIV. New Type of Temperature-sensitive Mutant

A group of temperature-sensitive mutants of phiX174 has been isolated which can go through a single, normal one-step growth cycle at 40 C but fail to form plaques at this temperature. Such mutants fail to initiate a second cycle at 40 C; however they can gain the capacity to infect at 40 C, upon incubation for 10 min in broth at 30 C. In regaining the ability to infect, the phage appear to undergo a temperature-dependent conformational alteration. The inverse process, a reversible loss of ability to infect at 40 C, is observed when such phage produced at 30 C are incubated for 2 hr at 40 C. The defect in initiation of a second cycle of infection appears to be in the injection of viral deoxyribonucleic acid. A two-step complementation test has been used to identify the cistron coding for the affected function. Such mutants are also unusually sensitive to an irreversible thermal inactivation when incubated at 40 C.     

New Type of Allergic Asthma due to IgG “Reaginic” Antibody

This study was undertaken to examine the possibility that IgE is not the only immunoglobulin responsible for immediate allergic reactions. A group of asthmatics were investigated in whom immediate allergic reactivity of the bronchi to common inhalant allergens had been confirmed by provocation tests. Their sera were fractionated and the reaginic activity of the immunoglobulin classes was studied by passive cutaneous anaphylaxis testing in monkeys. The results showed that the immediate allergic reactions were due to IgE antibodies in most patients, but there was a group with reactions due to short-term anaphylactic IgG antibodies. It was not possible to inhibit the IgG-mediated responses with disodium cromoglycate. As these two groups had clearly different serum IgE levels the estimation of IgE provided an important guide to the management of these patients.