Charge delocalization characteristics of regioregular high mobility polymers.

Controlling the regioregularity among the structural units of narrow bandgap conjugated polymer backbones has led to improvements in optoelectronic properties, for example in the mobilities observed in field effect transistor devices. To investigate how the regioregularity affects quantities relevant to hole transport, regioregular and regiorandom oligomers representative of polymeric structures were studied using density functional theory. Several structural and electronic characteristics of the oligomers were compared, including chain planarity, cation spin density, excess charges on molecular units and internal reorganizational energy. The main difference between the regioregular and regiorandom oligomers is found to be the conjugated backbone planarity, while the reorganizational energies calculated are quite similar across the molecular family. This work constitutes the first step on understanding the complex interplay of atomistic changes and an oligomer backbone structure toward modeling the charge transport properties.

Faster and easier radiochemical purity testing for [125I]sodium iothalamate.

A previous method for determination of the radiochemical purity (RCP) value of [125I]sodium iothalamate uses two paper strips and solvents (total developing time is approximately 2.5 h). To simplify and shorten the RCP testing procedure, our laboratory has developed a single-strip chromatography method that not only distributes free 125I and [125I]sodium iothalamate to different relative front (Rf) locations, but is also faster and easier to perform. RCP of [125I]sodium iothalamate was determined with the use of a 10-cm instant thin-layer chromatography strip impregnated with polysilicic acid gel (ITLC-SA) as the solid phase, and a mobile phase of 2-butanol:acetic acid:water (140:2.5:70, v/v). By using autoradiography and counting the strip segments in a gamma counter, our results indicated that free 125I migrated to Rf = 0.89-1.00 while the [125I]sodium iothalamate moved to Rf = 0.44-0.67. The total developing time for the single-strip ITLC-SA system was approximately 1 h.

Recombinant human osteogenic protein-1 (hOP-1) induces new bone formation in vivo with a specific activity comparable with natural bovine osteogenic protein and stimulates osteoblast proliferation and differentiation in vitro.

We reported previously that a 32-36-kDa osteogenic protein purified from bovine bone matrix is composed of dimers of two members of the transforming growth factor (TGF)-beta superfamily: the bovine equivalent of human osteogenic protein-1 (OP-1) and bone morphogenetic protein-2a, BMP-2a (BMP-2). In the present study, we produced the recombinant human OP-1 (hOP-1) in mammalian cells as a processed mature disulfide-linked homodimer with an apparent molecular weight of 36,000. Examination of hOP-1 in the rat subcutaneous bone induction model demonstrated that hOP-1 was capable of inducing new bone formation with a specific activity comparable with that exhibited by highly purified bovine osteogenic protein preparations. The half-maximal bone-inducing activity of hOP-1 in combination with a rat collagen matrix preparation was 50-100 ng/25 mg of matrix as determined by the calcium content of day 12 implants. Evaluation of hOP-1 effects on cell growth and collagen synthesis in rat osteoblast-enriched bone cell cultures showed that both cell proliferation and collagen synthesis were stimulated in a dose-dependent manner and increased 3-fold in response to 40 ng of hOP-1/ml. Examination of the expression of markers characteristic of the osteoblast phenotype showed that hOP-1 specifically stimulated the induction of alkaline phosphatase (4-fold increase at 40 ng of hOP-1/ml), parathyroid hormone-mediated intracellular cAMP production (4-fold increase at 40 ng of hOP-1/ml), and osteocalcin synthesis (5-fold increase at 25 ng of hOP-1/ml). In long-term (11-17 day) cultures of osteoblasts in the presence of beta-glycerophosphate and L(+)-ascorbate, hOP-1 markedly increased the rate of mineralization as measured by the number of mineral nodules per well (20-fold increase at 20 ng of hOP-1/ml). Direct comparison of TGF-beta 1 and hOP-1 in these bone cell cultures indicated that, although both hOP-1 and TGF-beta 1 promoted cell proliferation and collagen synthesis, only hOP-1 was effective in specifically stimulating markers of the osteoblast phenotype.

Bovine osteogenic protein is composed of dimers of OP-1 and BMP-2A, two members of the transforming growth factor-beta superfamily.

A bone-inductive protein has been purified from bovine bone and designated as osteogenic protein (OP). The purified OP induces new bone at less than 5 ng with half-maximal bone differentiation activity at about 20 ng/25 mg of matrix implant in a subcutaneous bone induction assay. The purified osteogenic protein is composed of disulfide-linked dimers that migrate on sodium dodecyl sulfate gels as a diffuse band with an apparent molecular weight of 30,000. Upon reduction, the dimers yield two subunits that migrate with molecular weights of 18,000 and 16,000. Both subunits are glycosylated. After chemical or enzymatic deglycosylation, the dimers migrate as a diffuse 27-kDa band that upon reduction yields two polypeptides that migrate at 16 kDa and 14 kDa, respectively. The carbohydrate moiety does not appear to be essential for biological activity since the deglycosylated proteins are capable of inducing bone formation in vivo. Amino acid sequences of peptides generated by proteolytic digestion show that the subunits are distinct but related members of the transforming growth factor-beta super-family. The 18-kDa subunit is the protein product of the bovine equivalent of the human OP-1 gene and the 16-kDa subunit is the protein product of the bovine equivalent of the human BMP-2A gene.

Characterization of microvascular cell cultures from normotensive and hypertensive rat brains: pericyte-endothelial cell interactions in vitro.

We used specific markers and fluorescence microscopy to identify and characterize cerebrovascular cells. Cultures were derived from brain microvessels isolated from normotensive (Wistar Kyoto, WKY) and spontaneously hypertensive (SHR) rat brains prior to, coincident with and following the onset of chronic hypertension. Endothelial cells were characterized using di-acyl LDL and non-muscle isoactin-specific antibodies. Cerebrovascular pericytes were identified with the anti-muscle and non-muscle actin antibody staining. Using this combination of cell culture and fluorescence localization, we have been able to demonstrate that brain pericytes are tightly associated with the endothelial cells of the hypertensive-prone and hypertensive cell cultures, but not with the normotensive endothelial cultures. While the endothelial-pericyte ratio in the hypertensive-prone microvascular cultures was between 5:1 and 10:1, the number of pericytes associated with the hypertensive rat brain cultures increased two to five times (2:1-1:1). Muscle and non-muscle actin antibody staining localized the spindle-shaped pericytes of the hypertensive microvascular colonies. Pericytes were found overlaying and encircling the endothelial cells. Normotensive pericytes were not endothelial-associated. Whereas the hypertensive pericyte is devoid of stress fibers, the normotensive pericyte is a larger, spread-out cell possessing numerous stress fibers rich in muscle and non-muscle actin. These results provide the first evidence that the etiology and inception of cerebrovascular disease may be pericyte-related and suggest that pericyte contraction could play a pivotal role in regulating the flow of blood within the brain microcirculation.