Path integral quantization corresponding to the deformed Heisenberg algebra

In this paper, the deformation of the Heisenberg algebra, consistent with both the generalized uncertainty principle and doubly special relativity, has been analyzed. It has been observed that, though this algebra can give rise to fractional derivative terms in the corresponding quantum mechanical Hamiltonian, a formal meaning can be given to them by using the theory of harmonic extensions of function. Depending on this argument, the expression of the propagator of the path integral corresponding to the deformed Heisenberg algebra, has been obtained. In particular, the consistent expression of the one dimensional free particle propagator has been evaluated explicitly. With this propagator in hand, it has been shown that, even in free particle case, normal generalized uncertainty principle and doubly special relativity show very much different result.     

Polyelectrolyte behavior and macromolecular properties of sodium amylopectin xanthate in dilute solution

Sodium amylopectin xanthate was prepared by xanthation of potato amylopectin in alkaline medium. The pure product was characterized by I₂ solution and ultraviolet spectra of the xanthate groups. The polyelectrolyte behavior of Na amylopectin xanthate in aqueous and salt solutions was investigated by viscometry and light scattering. Its polyelectrolyte behavior in aqueous solution as studied viscometrically was completely different from that of Na amylose xanthate, which is characteristic of linear polyelectrolyte molecules. This difference in behavior could be partly due to the branched structure of amylopectin molecule. A dissymmetry study of Na amylopectin xanthate in aqueous and salt solutions, however, showed that Na amylopectin xanthate molecule underwent expansion in water by about 1.3 times its linear dimension in 0.5M NaCl (unperturbed value). Light-scattering measurements confirmed that the Na amylopectin xanthate molecule had a polydisperse random-coil chain configuration in 0.25M NaCl. Its molecular weight, end-to-end length, and other parameters in salt and alkali solutions were also determined, and the data were then compared with those of Na amylose xanthate in the same media. The solution behavior of Na amylopectin xanthate in 1M NaOH was further investigated and linear expansion factor α, excluded volume factor A₂M _W/[η], and Flory's hydrodynamic constant φ were evaluated.     

Mechanism of azole antifungal activity as determined by liquid chromatographic/mass spectrometric monitoring of ergosterol biosynthesis

A liquid chromatography/mass spectrometry (LC/MS) method for separation and characterization of ergosterol biosynthetic precursors was developed to study the effect of Posaconazole on sterol biosynthesis in fungi. Ergosterol biosynthetic precursors were characterized from their electron ionization mass spectra acquired by a normal-phase chromatography, particle beam LC/MS method. Fragment ions resulting from cleavage across the D-ring and an abundant M - 15 fragment ion were diagnostic for methyl substitution at C-4 and C-14. Comparison of the sterol profile in control and treated Candida albicans incubations showed depletion of ergosterol and accumulation of C-4 and C-14 methyl-substituted sterols following treatment with Posaconazole. These C-4 and C-14 methyl sterols are known to be incapable of sustaining cell growth. The results demonstrate that Posaconazole exerts its antifungal activity by inhibition of ergosterol biosynthesis. Furthermore, Posaconazole appears to disrupt ergosterol biosynthesis by inhibition of lanosterol 14alpha-demethylase.     

Physicochemical and macromolecular properties of sodium amylose xanthate in dilute solution

Sodium amylose xanthate has been studied in dilute solution. Potato starch was fractionated for this purpose into amylose and amylopectin fractions. Amylose was xanthated in solution under alkaline conditions and the Na amylose xanthate was then characterized by reaction with I₂ solution and ultraviolet spectra of the xanthate groups determined. Stability of the xanthate in alkaline condition under both oxygen and nitrogen atmospheres was also investigated. From light scattering measurements of dilute salt solutions of Na amylose xanthate, the weight-average molecular weight M _w as well as the molecular dimensions were determined. In 0.11M NaCl, which conforms to the θ solvent, Na amylose xanthate molecules appear to have a random-coil configuration. Two other configurational parameters, such as the effective bond length b, and the steric factor σ, i.e., (R₀²)^1/2/(R_f² )^1/2, where (R₀²)^1/2 is the Root-mean-square end-to-end distance in the unperturbed state and (R_f² )^1/2 is the unperturbed value calculated on the assumption of free rotation about each intermonomer C? O bond of the amylose chain were also calculated and found to be 6.24 and 1.020, respectively. It is thus concluded that the amylose chain in Na amylose xanthate behaves as a typical flexible coil in dilute salt solution.     

Extraction and characterization of adenovirus

A new methodology for the extraction and characterization of proteins from Coomassie-stained sodium dodecylsulfate polyacrylamide gel electrophoresis using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) has been described. The utility of this methodology was demonstrated in the characterization of adenovirus proteins. The key steps in the extraction and destaining process involve washing the excised band with a combination of solvents that include 10% acetic acid, acetonitrile, methanol, and formic acid:water:isopropanol mixture. By using this procedure, we determined adenovirus proteins with molecular weights ranging from 10,000 to 110,000 Da by MALDI-MS, obtaining a detection limit of approximately 6 pmol. Parallel experiments were successfully carried out to analyze adenovirus proteins from Cu-stained gels. It was observed that increase in laser intensity resulted in significant improvements in the quality of MALDI mass spectra for the analysis of inefficiently destained proteins from Cu-stained gels.     

Influence of branch length asymmetry on the electrophoretic mobility of rigid rod-like DNA

The electrophoretic mobility of three-arm asymmetric star DNA molecules, produced by incorporating a short DNA branch at the midpoint of rigid-rod linear DNA fragments, is investigated in polyacrylamide gels. We determine how long the added branch must be to separate asymmetric star DNA from linear DNA with the same total molecular weight. This work focuses on two different geometric progressions of small DNA molecules. First, branches of increasing length were introduced at the center of a linear DNA fragment of constant length. At a given gel concentration, we find that relatively small branch lengths are enough to cause a detectable reduction in electrophoretic mobility. The second geometric progression starts with a small branch on a linear DNA fragment. As the length of this branch is increased, the DNA backbone length is decreased such that the total molar mass of the molecule remains constant. The branch length was then increased until the asymmetric branched molecule becomes a symmetric three-arm star polymer, allowing the effect of molecular topology on mobility to be studied independent of size effects. DNA molecules with very short branches have a mobility smaller than linear DNA of identical molar mass. The reason for this change in mobility when branching is introduced is not known, however, we explore two possible explanations in this article. (i) The branched DNA could have a greater interaction with the gel than linear DNA, causing it to move slower; (ii) the linear DNA could have modes of motion or access to pores that are unavailable to the branched DNA.     

Fast-atom bombardment and tandem mass spectrometry of macrolide antibiotics

Molecular weights of macrolide antibiotics can be determined from either (M + H)⁺ or (M + Met)⁺, the latter desorbed from alkali metal salt-saturated matrices. The ion chemistry of macrolides, as determined by tandem mass spectrometry (MS/MS), is different for ions produced as metallated than those formed as (M + H)⁺ species. An explanation for these differences is the location of the charge. For protonated species, the charge is most likely situated on a functional group with high proton affinity, such as the dimethylamino group of the ammo sugar. The alkali metal ion, however, is bonded to the highly oxygenated aglycone. As a result, the collision-activated dissociation spectra of protonated macrolides are simple with readily identifiable fragment ions in both the high and low mass regions but no fragments in the middle mass range. In contrast, the cationized species give complex spectra with many abundant ions, most of which are located in the high mass range. The complementary nature of the fragmentation of these two species recommends the study of both by MS/MS when determining the structure or confirming the identity of these biomaterials.     

Study of approximate coupled cluster methods for first-order static properties

In this paper, we analyse the algebraic structure of the equations for calculating the first order static properties using several approximate versions of Coupled Cluster (CC) methods. In particular, the non-variational and the variational method using a CC wavefunction corresponding to an appropriately defined perturbed Hamiltonian as well as the simple expectation value expression using a CC stationary state are studied under different approximations. Two different models are proposed: (a) use of maximum overlap orbitals where the pertinent approximations are TT ₂, T ⁽¹⁾ T ₂ ⁽¹⁾, (b) use of Hartree-Fock orbitals and T(T ₁+T ₂), T ⁽¹⁾(T ₁ ⁽¹⁾ +T ₂ ⁽¹⁾ ) approximations. It is analytically shown that in both these models certain approximate versions of the methods under purview yield identical results for first order static properties.NCL Communication No. 3725     

Kinetics and mechanism of reactions of bis(biguanide)copper(II) ion with 2,2′-bipyridyl and 1,10-phenanthroline in aqueous solution

Summary In aqueous solution [Cu(bigH)₂]²⁺ (bigH=biguanide) reacts with 2,2-bipyridyl (bipy) and 1,10-phenanthroline (phen) through intermediate formation of ternary complexes [Cu(bigH)(L)]²⁺ and [Cu(bipy)(phen)]²⁺ and binary complexes [CuL₂]²⁺ (L=bipy, phen). The rates of the different steps have been followed in borax buffer (pH 8.0±0.1) by stopped-flow spectrophotometry. For each step k_obs=k₀+k_L[L] and the k_L path appears to be associative. H and S values for the k_L path conform to an isokinetic trend.