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Hydrophilic Side Chains (hydrophilic + side_chain)
Selected AbstractsCapillary electrophoresis of amphipathic ,-helical peptide diastereomersELECTROPHORESIS, Issue 1 2004Traian V. Popa Abstract We have made a rigorous assessment of the ability of capillary electrophoresis to resolve peptide diastereomers through its application to the separation of a series of synthetic 18-residue, amphipathic ,-helical monomeric peptide analogues, where a single site in the centre of the hydrophobic face of the ,-helix is substituted by 19 L - or D -amino acids. Such L - and D -peptide pairs have the same mass-to-charge ratio, amino acid sequence and intrinsic hydrophobicity, varying only in the stereochemistry of one residue. CE approaches assessed in their ability to separate diastereomeric peptide pairs included capillary zone electrophoresis (uncoated capillary), micellar electrokinetic chromatography (uncoated capillary in the presence of 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, CHAPS), open-tubular capillary electrochromatography (C8 -coated capillary in the presence of 25% 2,2,2-trifluoroethanol (TFE) or 25% ethanol). Overall, the OT-CEC methods were the most effective at separating the most peptide pairs, particularly for those containing hydrophilic side chains. However, the MEKC approach proved most effective for separation of peptide pairs containing hydrophobic or aromatic side chains. [source] Calcium phosphate cement reinforced by polypeptide copolymersJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2006Jiaping Lin Abstract Water-based calcium phosphate with bone repairing capability was reinforced by polypeptide graft copolymers and micelles that were formed by polypeptide copolymers. The mechanical studies showed that the compression strength and fracture energy of the calcium phosphate cement (CPC)/polypeptide composites are appreciably higher than those of CPC. The molecular structure of the polypeptide graft copolymers and the association form of the polypeptide copolymers exhibit a marked effect on the mechanical properties of CPC/polypeptide composites. The polypeptide copolymers with more hydrophilic side chains and with core-shell micelle forms have more effective reinforcement effect. The morphological studies based on the scanning electron microscope (SEM) observations revealed that both polypeptide graft copolymers and polypeptide copolymer micelles are well dispersed in CPC matrix. According to the obtained experimental results, reinforcement mechanism was suggested. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Cationic, water-soluble, fluorene-containing poly(arylene ethynylene)s: Effects of water solubility on aggregation, photoluminescence efficiency, and amplified fluorescence quenching in aqueous solutionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2006Yan-Qin Huang Abstract Three novel fluorene-containing poly(arylene ethynylene)s with amino-functionalized side groups were synthesized through the Sonogashira reaction. They were poly{9,9-bis[6,-(N,N -diethylamino)hexyl]-2,7-fluorenylene ethynylene}- alt - co -{2,5-bis[3,-(N,N -diethylamino)-1,-oxapropyl]-1,4-phenylene} (P1), poly{9,9-bis[6,-(N,N -diethylamino)hexyl]-2,7-fluorenylene ethynylene} (P2), and poly({9,9-bis[6,-(N,N -diethylamino)hexyl]-2,7-fluorenylene ethynylene}- alt - co -(1,4-phenylene)) (P3). Through the postquaternization treatment of P1,P3 with methyl iodide, we obtained their cationic water-soluble conjugated polyelectrolytes (WSCPs): P1,,P3,. The water solubility was gradually improved from P3, to P1, with increasing contents of hydrophilic side chains. After examining the ultraviolet,visible absorption and photoluminescence (PL) spectra, fluorescence lifetimes, and dynamic light scattering data, we propose that with the reduction of the water solubility from P1, to P3,, they exhibited a gradually increased degree of aggregation in H2O. The PL quantum yields of P1,,P3, in H2O displayed a decreasing tendency consistent with the increased degree of aggregation, suggesting that the pronounced degree of aggregation was an important reason for the low PL quantum yields of WSCPs in H2O. Two structurally analogous water-soluble trimers of P2, and P3,, model compounds 2,7-bis(9,,9,-bis{6,-[(N,N -diethyl)- N -methylammonium] hexyl}-2,-fluorenylethynyl)-9,9-bis{6,-[(N,N -diethyl)- N -methylammonium]hexyl}fluorene hexaiodide and 1,4-bis(9,,9,-bis{6,-[(N,N -diethyl)- N -methylammonium]hexyl}-2,-fluorenylethynyl)benzene tetraiodide, were synthesized. The amplified fluorescence quenching of these WSCPs by Fe(CN)64, in H2O was studied by comparison with a corresponding analogous trimer. The effects of aggregation on the fluorescence quenching may be two-edged in these cases. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5778,5794, 2006 [source] Novel Amphiphilic Degradable Poly(, -caprolactone)- graft -poly(4-vinyl pyridine), Poly(, -caprolactone)- graft -poly(dimethylaminoethyl methacrylate) and Water-Soluble DerivativesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 9 2008Benjamin Nottelet Abstract New amphiphilic graft copolymers that have a poly(, -caprolactone) (PCL) biodegradable hydrophobic backbone and poly(4-vinylpyridine) (P4VP) or poly(2-(N,N- dimethylamino)ethyl methacrylate) (PDMAEMA) hydrophilic side chains have been prepared by anionic polymerization of the corresponding 4VP and DMAEMA monomers using a PCL-based macropolycarbanion as initiator. The water solubility of these amphiphilic copolymers is improved by quaternization, which leads to fully water-soluble cationic copolymers that give micellar aggregates in deionized water with diameters ranging from 65 to 125 nm. In addition, to improve the hydrophilicity of PCL- g -P4VP, grafting of poly(ethylene glycol) (PEG) segments has been carried out to give a water-soluble double grafted PCL- g -(P4VP;PEG) terpolymer. [source] De novo proteins from designed combinatorial librariesPROTEIN SCIENCE, Issue 7 2004Michael H. Hecht Abstract Combinatorial libraries of de novo amino acid sequences can provide a rich source of diversity for the discovery of novel proteins with interesting and important activities. Randomly generated sequences, however, rarely fold into well-ordered proteinlike structures. To enhance the quality of a library, features of rational design must be used to focus sequence diversity into those regions of sequence space that are most likely to yield folded structures. This review describes how focused libraries can be constructed by designing the binary pattern of polar and nonpolar amino acids to favor proteins that contain abundant secondary structure, while simultaneously burying hydrophobic side chains and exposing hydrophilic side chains to solvent. The "binary code" for protein design was used to construct several libraries of de novo proteins, including both ,-helical and ,-sheet structures. The recently determined solution structure of a binary patterned four-helix bundle is well ordered, thereby demonstrating that sequences that have neither been selected by evolution (in vivo or in vitro) nor designed by computer can form nativelike proteins. Examples are presented demonstrating how binary patterned libraries have successfully produced well-ordered structures, cofactor binding, catalytic activity, self-assembled monolayers, amyloid-like nanofibrils, and protein-based biomaterials. [source] Conformational Stability of Bovine Serum Albumin in Aqueous Amides: A Further Insight into the Mechanism of Urea Acting on the ProteinCHINESE JOURNAL OF CHEMISTRY, Issue 6 2010Lin Ma Abstract The binding distances of fluorescein to bovine serum albumin (BSA) in formamide-water and N,N -dimethyl- formamide-water mixtures were determined by fluorescence quenching method and compared with the values in urea-water mixtures in our previous work. The results, together with the analysis of fluorescence spectra, were utilized to probe the conformational stability of protein in aqueous amides, providing a further insight into the mechanism of urea acting on protein. The spectral properties of BSA showed significant difference in the aqueous solutions of the three kinds of amide and indicated that both NH2 group and C=O group could form hydrogen bond with the protein, serving as donor and acceptor, respectively. However, the results revealed that the multiple hydrogen bonds of NH2 group with back bond and hydrophilic side chains of the protein played a key role in the nonspecific urea-mediated network of intramolecular interaction due to its higher hydrogen bonding capability compared to C=O group. [source] | |||||||||||||