Marshall David Crew

Hydroxypropyl Methylcellulose Acetate Succinate-Based Spray-Dried Dispersions: An Overview

Spray-dried dispersions (SDDs) of low-solubility drugs have been prepared using the polymer hydroxypropyl methylcellulose acetate succinate (HPMCAS). For a variety of drug structures, these SDDs provide supersaturation in in vitro dissolution determinations and large bioavailability increases in vivo. In bile-salt/lecithin in vitro solutions, these SDDs provide amorphous drug/polymer colloids and an increased concentration of free drug and drug in micelles relative to crystalline or amorphous drug. As dry powders, the SDDs are a single amorphous phase in which the drug remains amorphous and dispersed and does not crystallize over storage times relevant for practical drug products. A melting temperature (Tm)/glass-transition temperature (Tg) (K/K) versus log P map for 139 compounds formulated as SDDs provides a perspective on an appropriate formulation strategy for low-solubility drugs with various physical properties.

Glycogen phosphorylase inhibitor

Type 2 diabetes is a complex metabolic disease with hyperglycemia as its recognizable hallmark. Hepatic glucose output is elevated in Type 2 diabetic patients, and evidence suggests drugs which lower hepatic glucose production are effective antihyperglycemic agents. Glycogenolysis, which is the release of monomeric glucose from its polymeric storage form called glycogen, is a key contributor to hepatic glucose output. Glycogen phosphorylase is the enzyme that catalyzes this process. This review covers advances in the design of small molecule inhibitors of this enzyme, their biological activity, and their potential as effective antihyperglycemic agents for the treatment of Type 2 diabetes.

Long holographic lifetimes in bacteriorhodopsin films

The D85N genetic variant of bacteriorhodopsin (BR) displays a nearly permanent lifetime of the photochromic P(490) state. We present pump-probe measurements that demonstrate this behavior. However, diffraction efficiency measurements made from holograms recorded in a hydrated D85N film show markedly different decay behavior, suggesting that a molecular diffusion process is occurring in the film. Holograms recorded with different grating frequencies display correspondingly different decay times, thus supporting this hypothesis. A thin D85N film was fabricated that was chemically cross linked, resulting in the elimination of diffusion of BR molecules within the polymer matrix. This film exhibits a grating lifetime of the order of weeks or more, thus permitting the long-term holographic storage of information.

Bit-error-rate issues for holographic data storage in bacteriorhodopsin films

Photochromic films made from bacteriorhodopsin (BR) possess many desirable characteristics for a candidate holographic optical data storage medium. These properties include optical erasability, high spatial resolution, adequate diffraction efficiency, flexible film formats, durability, an optimal recording/readout wavelength of about 680 - 690 nm, and potentially inexpensive cost. In this paper, we experimentally study the raw bit-error-rate (BER) achievable with BR films made from the genetic variant known as D85N. Experimental data is collected for digital bit patterns fabricated as chrome-on- glass masks, at two different spatial resolutions. The results show that films fabricated from D85N have good potential for use in holographic data storage systems, but that further effort must be devoted to the film fabrication process in order to minimize optical nonuniformity and scattering losses.