Novalac resin (N) with hexamethylenetetramine (HTA) was cured with biomass (B) or Kraft lignin (KL) or hydroxymethylated Kraft lignin (KLH) or cellulose (CEL). The agriculturalfindustrial by-product of olive stones was used as biomass. Kraft lignin, hydroxymethylated Kraft lignin and cellulose were isolated from the biomass. The cure was followed by DSC and IR spectroscopy. Based on the IR spectra of cured materials and their characteristic bands, the proportion of N/B = 50/50 was chosen for the preparation of novolac mixtures with other components. Only N-KLH exhibited values of AH higher than AH,, calculated from the law of mixtures, indicating that KLH participates in the cure reaction. The kinetic parameters E and k, of the total cure reactions, calculated by DSC scans, increased in the order N < N-KLH < N-B < N-KL < N-CEL.The incorporation of KLH in the mass of N-HTA led to a slight increase in E and k,. On the other hand, KL, CEL and B acted as diluents in the mass of novolac. Generally, the cure of all materials was a first order reaction, indicating that the cure mechanism of novolac remains the same.
A convenient method of synthesis, using a combination of solid and liquid phase methodology, for locust Adipokinetic Hormone-I (AKH-I) and its analogues with modifications at the threonine residues are reported. The N-terminal nonapeptide acid of AKH-I is synthesized in the solid phase using the 2-chlorotrityl chloride resin and the Fmoc/t-Bu strategy. Quantitative cleavage of the nonapeptide acid from the resin, with the tert-butyl type side-chain protection intact, is achieved with a mixture of acetic acid/trifluoroethanol/ dichloromethane. The nonapeptide acid is then coupled in solution to the threonine derivatives, H-Thr-NH2 or H-Thr(Bz1)-NH2, with the DCCiHOBt method. The efficiency of this approach in the synthesis of AKH-I is demonstrated by the high yields and purity of the synthesized peptides. All the synthesized peptides were tested in two ways: first, in a lipid mobilization assay in locusts in vivo; and second, in a novel assay in vitro concerned with the uptake of radiolabelled acetate into locust tissue. Replacement of the hydroxyl hydrogen in Thr5 of locust AKH-I by the bulky and highly lipophilic tert-butyl group reduced the potency markedly, whereas efficacy is unaffected, but when the hydroxyl hydrogen of Thr'O in AKH-I is replaced by a benzyl group, the activity of the resulting analogue is identical to that of the natural peptide. Structure-activity relationships are discussed. @ Munksgaard 1994.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.