Human Complement Component 8g ELISA Kit

Langmuir monolayers of two artificial cyclic peptides with an alternating sequence of L-glutamic acid and 3-aminobenzoic acid subunits, a cyclohexapeptide (C6G) and a cyclooctapeptide (C8G), were investigated using a variety of techniques, including pi-A isotherms, in situ surface sum-frequency generation (SFG) and Brewster angle microscopy. The monolayers were also transferred onto a solid substrate by the Langmuir-Blodgett technique and characterized by grazing incident X-ray diffraction (GIXD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The investigations indicated that C6G forms 2D crystallite structures at the air-water interface, whereas no such structures were observed for C8G. Being amphiphilic, both peptides attain a horizontal orientation on the water surface after spreading. Surface compression causes the molecules to flip to a perpendicular state, thus minimizing the molecular area. The measurements also indicate that, in the perpendicular state, self-assembly of C6G leads to a tubular arrangement of the peptide rings. According to GIXD and TEM data, pairs of tubes arrange in a well defined and oriented order producing 2D crystals. Surface vibrational spectroscopic methods (sum-frequency generation and polarization modulation IR reflection-absorption) combined with molecular modeling gave insight into the arrangement of individual C6G molecules in the tubes. Overall, our results indicated that the tubular assembly of C6G is most likely due to intermolecular H-bonding between the CO group in the glutamic acid side chains and peptide NH group of a neighboring peptide ring.

The three chains of the human complement component C8 - alpha, beta and gamma - are encoded by distinct structural genes. C8A and C8B are closely linked on chromosome 1p and C8G is located on chromosome 9q. The biosynthesis and regulation of the gene products were studied in the human hepatoma-derived cell line HepG2 after in vitro induction of the acute-phase response by incubation with the cytokine interleukin IL-6. Analysis of C8 expression by immunoprecipitation and SDS-PAGE of biosynthetically labeled alpha-gamma and beta subunits demonstrated a positive response to this cytokine. The expression pattern observed in the hepatoma cells characterizes C8 in vitro as a positive acute-phase protein. In addition, the comparison of the relative amounts of the C8 transcripts provides evidence for a post transcriptional regulation of the C8 beta subunit. No evidence was obtained for an increased expression of IL-6 or IL-6 receptor mRNA thus excluding autoregulatory mechanisms of the cytokine in HepG2 cells.