Pick your polymer: The reactivity ratios, r, of the comonomers can be controlled by the configuration of the active species in the copolymerization of ε‐caprolactone (CL) and l,l‐lactide (LA; see scheme). Thus, by varying the configuration of the initiator, a broad spectrum of copolymers with different microstructures, from gradient to more random, can be prepared in a controlled way.
L,L‐lactide (LA) and ε‐caprolactone (CL) block copolymers have been prepared by initiating the poly(ε‐caprolactone) (PCL) block growth with living poly(L,L‐lactide) (PLA*). In the previous attempts to prepare block copolymers this way only random copolyesters were obtained because the PLA* + CL cross‐propagation rate was lower than that of the PLA–CL* + PLA transesterification. The present paper shows that application of Al‐alkoxide active centers that bear bulky diphenolate ligands results in efficient suppression of the transesterification. Thus, the corresponding well‐defined di‐ and triblock copolymers could be prepared.magnified image
Rheumatoid arthritis (RA) is a chronic inflammatory disease in which cytokines play an important role. The aim of the present study was to evaluate the -590 IL-4 promoter polymorphism in patients with RA and its association with disease activity and severity. We enrolled 94 patients with RA diagnosed according to the criteria of the American College of Rheumatology. Polymerase chain reaction amplification was used for analysis of the polymorphism at position -590 of the promoter of the IL-4 gene. The distribution of IL-4 genotypes in RA patients did not differ from control subjects. Nevertheless, the active form of RA was more frequently diagnosed in patients with T allele (genotypes CT and TT) as compared with homozygous CC patients. Moreover, in carriers of the T allele, parameters of disease activity (DAS 28 score, ESR, number of swollen and tender joints) were significantly increased. We suggest that the IL-4 -590 promoter polymorphism may be a genetic risk factor for RA severity.
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