Aequorin mutants with increased thermostability

Bioluminescent labels can be especially useful for in vivo and live animal studies due to the negligible bioluminescence background in cells and most animals, and the non-toxicity of bioluminescent reporter systems. Significant thermal stability of bioluminescent labels is essential, however, due to the longitudinal nature and physiological temperature conditions of many bioluminescent-based studies. To improve the thermostability of the bioluminescent protein aequorin, we employed random and rational mutagenesis strategies to create two thermostable double mutants, S32T/E156V and M36I/E146K, and a particularly thermostable quadruple mutant, S32T/E156V/Q168R/L170I. The double aequorin mutants, S32T/E156V and M36I/E146K, retained 4 and 2.75 times more of their initial bioluminescence activity than wild-type aequorin during thermostability studies at 37 °C. Moreover, the quadruple aequorin mutant, S32T/E156V/Q168R/L170I, exhibited more thermostability at a variety of temperatures than either double mutant alone, producing the most thermostable aequorin mutant identified thus far.     

Synthesis of sugar oxime ether surfactants

A straightforward synthesis of a novel class of sugar surfactants is described. The key step is the chemoselective condensation of a hydrophobic alkoxyamine with the resident aldehyde/ketone moiety on a hydrophilic sugar. Neither protection/deprotection of the sugars nor extensive product purification is required. The method allows for the facile adjustment of hydrophobic and hydrophilic domains of the sugar oxime ether surfactant and uses inexpensive, readily accessible, and renewable materials.     

On the Motion of a Dynamic System with Minimal Dissipation

The motion of a holonomic scleronomic non-conservative mechanicalsystem with minimal dissipation is considered. As applicationsof the theory several problems are studied in detail.     

Modelling the initial motion of large cylindrical and spherical bubbles

A two-dimensional, transient, finite difference technique based on a volume fraction specification of the free surface position and accounting for the effects of surface tension is shown to accurately predict the initial motion of large cylindrical and spherical bubbles. The predictions compare very favourably with the experimental data of Walters and Davidson. The initial acceleration of cylindrical and spherical bubbles is properly predicted as g and 2g respectively. The penetration of a tongue of liquid from below is the dominant process by which large deformations from the original shape take place and is well predicted by the model in both cases. For the spherical case the eventual transition into a toroidal bubble is demonstrated and the circulation associated with a rising toroidal bubble as a function of its volume upon release is shown to agree very well with experiments. Iterative linear equation-solving techniques applicable to the special nature of the linear system resulting from such a free surface specification are surveyed and a simple Jacobi iteration based on red-black ordering is found to perform well. The impact of the free surface on the relaxation of the linear system and the convergence criteria is also explored.     

Synthesis of 5-benzyl and 5-benzyloxybenzyl-3′-azido-2′,3′-dideoxyuridine and their analogues as potential anti-AIDS agents

5-Benzyl and 5-benzyloxybenzyl-substituted 3′-azido-2′,3′-dideoxyuridine, ( 8a and 8b ), 3′-halogeno-2′,3′-dideoxyuridine, 9a, 9b, 10a, 10b, 11a and 11b , and 2′,3′-dideoxyuridine, 12a and 12b , of Scheme I were synthesized as potential anti AIDS agents. Synthesis of epimers of 8a and 8b , 5-benzyl- and 5-benzyloxybenzyl-1-(3′-azido-2′,3′-dideoxy-β-D-threo-pentafuranosyl)uracil, 15a and 15b , and 5-benzyl- and 5-benzyloxy-5′-azido-2′,5′-dideoxyuridine, 16a and 16b , shown in Scheme II, were also reported.     

Photoemission and energy loss spectroscopy on semiconductor surfaces

The application of multiple experimental techniques to silicon surface studies is discussed. Two specific cases are considered: the chemisorption of oxygen on silicon at coverages up to one monolayer and the intrinsic surface states on cleaved and on annealed Si (111) surfaces. It is shown that by combining electron energy loss spectroscopy and ultraviolet photoemission spectroscopy, one can obtain an approximate energy level model for both occupied and unoccupied states     

Calculations of the giant dipole resonance for sd-shell nuclei in the open-shell random phase approximation

The systematics of the giant dipole resonance have been calculated in the open-shell RPA for all the self-conjugate sd-shell nuclei, using (i) a phenomenological Rosenfeld interaction, (ii) Barret, Hewitt and McCarthy G-matrix elements and (iii) Kuo G-matrix elements. The excitations are based on shell model ground states for all nuclei except ²⁸Si for which a projected Hartree-Fock ground state was used.