Non-linear vibrations of a harmonically excited autoparametric system

Harmonic forced vibration of a spring-mass-damper system with a parametrically excited pendulum hinged to the mass is investigated. Two types of restoring forces on the pendulum are considered. The method of harmonic balance is used to evaluate the system response. The results are also verified by numerical integration. Non-periodic system responses are possible if the excitation parameter is large. The performance of the pendulum as an absorber is also studied.     

Measuring the top quark mass in the eµ channel: A study

We describe a simple method to measure the top quark mass in the channel that may be useful in Run II of D? detector. The method is validated by applying it to the Run Ib eμ data.     

Age-related waning of in vitro Interferon-γ levels against r32kDaBCG in BCG vaccinated children

Background  

Mycobacterium bovis BCG vaccine has displayed inconsistent efficacy in different trials conducted in various geographical regions. Nevertheless, it significantly reduces the risk of severe childhood tuberculosis and continues to be used to prevent tuberculosis in many countries. Many studies revealed that efficacy of vaccine wanes with age. Most of the studies were based on in vivo and in vitro responses to tuberculin. With the advent of newer tests such as in vitro interferon-γ assays and identification of potent immunogenic mycobacterial proteins there is a need to corroborate the observations. This study aims at ascertaining the need for a booster at a later age as indicated by in vitro release of IFN-γ while evaluating Ag85A as an antigen.     

Determining the global DNA methylation status of rat according to the identifier repetitive elements

A large portion of the genome represents repetitive elements. Identifier (ID) elements, the major elements of short interspersed repetitive elements, are widespread with about 150 000 copies in the rat genome. Each ID element contains six CpG dinucleotides, which might account for the global methylation status of rat. We validated the CpG methylation of the ID elements by various methods. The methylation of one CpG site (CpG-3) of the ID element was investigated by performing pyrosequencing. The methylation percentage of the CpG-3 site was 53.6% (SD = 2.2) on average from six rat tissues with blood, but 24.6% (SD = 1.0) in rat pheochromocytoma, PC-12, cell line. This CpG-3 methylation was further verified by whole genome amplification (WGA), 5-azacytidine treatment, and proportional mixing of rat WGA genomic DNA (gDNA) with liver gDNA. Methylation-sensitive restriction enzyme PCR method showed that three other CpG sites (CpG-1, CpG-4, and CpG-5) within the ID element were also methylated (about 60%) in rat gDNA, but not in WGA gDNA. The ID elements may be good candidates for routine analysis of the global DNA methylation changes of rat for pharmaceutical treatment and their use can make basic epigenetic research possible with high accuracy.     

Recognition of isozymes via lanthanide ion incorporated polymerized liposomes

We report the selective recognition of carbonic anhydrase isozymes based on the excited-state lifetimes of chelated Eu(3+) ions incorporated in polymerized liposomes.     

Structural analysis of charge discrimination in the binding of inhibitors to human carbonic anhydrases I and II

Despite the similarity in the active site pockets of carbonic anhydrase (CA) isozymes I and II, the binding affinities of benzenesulfonamide inhibitors are invariably higher with CA II as compared to CA I. To explore the structural basis of this molecular recognition phenomenon, we have designed and synthesized simple benzenesulfonamide inhibitors substituted at the para position with positively charged, negatively charged, and neutral functional groups, and we have determined the affinities and X-ray crystal structures of their enzyme complexes. The para-substituents are designed to bind in the midsection of the 15 A deep active site cleft, where interactions with enzyme residues and solvent molecules are possible. We find that a para-substituted positively charged amino group is more poorly tolerated in the active site of CA I compared with CA II. In contrast, a para-substituted negatively charged carboxylate substituent is tolerated equally well in the active sites of both CA isozymes. Notably, enzyme-inhibitor affinity increases upon neutralization of inhibitor charged groups by amidation or esterification. These results inform the design of short molecular linkers connecting the benzenesulfonamide group and a para-substituted tail group in "two-prong" CA inhibitors: an optimal linker segment will be electronically neutral, yet capable of engaging in at least some hydrogen bond interactions with protein residues and/or solvent. Microcalorimetric data reveal that inhibitor binding to CA I is enthalpically less favorable and entropically more favorable than inhibitor binding to CA II. This contrasting behavior may arise in part from differences in active site desolvation and the conformational entropy of inhibitor binding to each isozyme active site.     

Development of an affinity silica monolith containing alpha1-acid glycoprotein for chiral separations

An affinity monolith based on silica and containing immobilized alpha(1)-acid glycoprotein (AGP) was developed and evaluated in terms of its binding, efficiency and selectivity in chiral separations. The results were compared with data obtained for the same protein when used as a chiral stationary phase with HPLC-grade silica particles or monoliths based on a copolymer of glycidyl methacrylate (GMA) and ethylene dimethacrylate (EDMA). The surface coverage of AGP in the silica monolith was 18% higher than that obtained with silica particles and 61% higher than that measured for a GMA/EDMA monolith. The higher surface area of the silica monolith gave materials that contained 1.5- to 3.6-times more immobilized protein per unit volume when compared to silica particles or a GMA/EDMA monolith. The retention, efficiency and resolving power of the AGP silica monolith were evaluated by injecting two chiral analytes onto this column (i.e., R/S-warfarin and R/S-propranolol). In each case, the AGP silica monolith gave higher retention plus better resolution and efficiency than AGP columns containing silica particles or a GMA/EDMA monolith. The AGP silica monolith also gave lower back pressures and separation impedances than these other materials. It was concluded that silica monoliths can be valuable alternatives to silica particles or GMA/EDMA monoliths when used with AGP as a chiral stationary phase.