Effects of chain length on oligopeptide hydrogelation

The co-assembly of mutually complementary, but self-repulsive oligopeptide pairs into viscoelastic hydrogels has been studied. Oligopeptides of 6, 10, and 14 amino acid residues were used to investigate the effects of peptide chain length on the structural and mechanical properties of the resulting hydrogels. Biophysical characterizations, including dynamic rheometry, small-angle X-ray scattering (SAXS) and fluorescence spectroscopy, were used to investigate hydrogelation at the bulk, fiber, and molecular levels, respectively. Upon mixing, the 10-mer peptides and the 14-mer peptides both form hydrogels while the 6-mer peptides do not. SAXS studies point to morphological similarity of the cross-sections of fibers underlying the 10 : 10 and 14 : 14 gels. However, fluorescence spectroscopy data suggest tighter packing of the amino acid side chains in the 10 : 10 fibers. Consistent with this tighter packing, dynamic rheometry data show that the 10 : 10 gel has much higher elastic modulus than the 14 : 14-mer (18 kPa vs. 0.1 kPa). Therefore, from the standpoint of mechanical strength, the optimum peptide chain length for this class of oligopeptide-based hydrogels is around 10 amino acid residues. © 2010, Royal Society of Chemistry

Effect of temperature during assembly on the structure and mechanical properties of peptide-based materials.

Mutually complementary, self-repulsive oligopeptide pairs were designed to coassemble into viscoelastic hydrogels. Peptide engineering was combined with biophysical techniques to investigate the effects of temperature on the structural and mechanical properties of the resulting hydrogels. Biophysical characterizations, including dynamic rheometry, small-angle X-ray scattering (SAXS), and fluorescence spectroscopy, were used to investigate hydrogelation at the bulk, fiber, and molecular levels, respectively. It has been found that temperature has a significant effect on the structure and mechanical properties of peptide-based biomaterials. Oligopeptide fibers assembled at 25°C are formed faster and are two times thicker, and the resulting material is mechanically seven times stronger than that assembled at 5°C. © 2010, American Chemical Societ

c-Myc Is Essential to Prevent Endothelial Pro-Inflammatory Senescent Phenotype

The proto-oncogene c-Myc is vital for vascular development and promotes tumor angiogenesis, but the mechanisms by which it controls blood vessel growth remain unclear. In the present work we investigated the effects of c-Myc knockdown in endothelial cell functions essential for angiogenesis to define its role in the vasculature. We provide the first evidence that reduction in c-Myc expression in endothelial cells leads to a pro-inflammatory senescent phenotype, features typically observed during vascular aging and pathologies associated with endothelial dysfunction. c-Myc knockdown in human umbilical vein endothelial cells using lentivirus expressing specific anti-c-Myc shRNA reduced proliferation and tube formation. These functional defects were associated with morphological changes, increase in senescence-associated-β-galactosidase activity, upregulation of cell cycle inhibitors and accumulation of c-Myc-deficient cells in G1-phase, indicating that c-Myc knockdown in endothelial cells induces senescence. Gene expression analysis of c-Myc-deficient endothelial cells showed that senescent phenotype was accompanied by significant upregulation of growth factors, adhesion molecules, extracellular-matrix components and remodeling proteins, and a cluster of pro-inflammatory mediators, which include Angptl4, Cxcl12, Mdk, Tgfb2 and Tnfsf15. At the peak of expression of these cytokines, transcription factors known to be involved in growth control (E2f1, Id1 and Myb) were downregulated, while those involved in inflammatory responses (RelB, Stat1, Stat2 and Stat4) were upregulated. Our results demonstrate a novel role for c-Myc in the prevention of vascular pro-inflammatory phenotype, supporting an important physiological function as a central regulator of inflammation and endothelial dysfunction

The relationship between dimensions of love, personality, and relationship length

The present study examined the associations among participant demographics, personality factors, love dimensions, and relationship length. In total, 16,030 participants completed an internet survey assessing Big Five personality factors, Sternberg’s three love dimensions (intimacy, passion, and commitment), and the length of time that they had been involved in a relationship. Results of structural equation modeling (SEM) showed that participant age was negatively associated with passion and positively associated with intimacy and commitment. In addition, the Big Five factor of Agreeableness was positively associated with all three love dimensions, whereas Conscientiousness was positively associated with intimacy and commitment. Finally, passion was negatively associated with relationship length, whereas commitment was positively correlated with relationship length. SEM results further showed that there were minor differences in these associations for women and men. Given the large sample size, our results reflect stable associations between personality factors and love dimensions. The present results may have important implications for relationship and marital counseling. Limitations of this study and further implications are discussed