Lipase-catalysed kinetic resolution of ethyl D,L-2-amino-4-phenylbutyrate by hydrolysis

Of 25 commercial lipases, nine were able to catalyse the hydrolysis of ethyl D,L-2-amino-4-phenylbutyrate (D,L-APBAE) to optically active D-APBAE, an intermediate for the synthesis of inhibitors of angiotensin-converting enzyme, with specific selectivity ranging between 3.7 and 12.5. Optimal conditions for porcine pancrease lipase-catalyzed reaction gave a 68% conversion and the D-ester was obtained by a simple extraction with an optical purity of 98%. Saponification of the ethyl ester of D-APBA in 1 M NaOH gave the optically active D-APBA with a chemical purity greater than 99%.     

Inhibition of lipase-catalyzed hydrolysis of sunflower oil in AOT/isooctane reversed micelles

The hydrolysis of sunflower oil using Candida cylindracea lipase in reversed micelles of AOT/isooctane was investigated. The inhibition caused by substrate and hydrolysis products has been found in the process of reaction. It was revealed that the extent of inhibition caused by oleic acid was higher than that caused by glycerol, and was much more serious in the case of the mixture of hydrolysis products. Moreover, with the initial addition of glycerol into the reaction mixture, the stability of lipase could be increased during the hydrolysis of sunflower oil in reversed micelles. We thank the National Natural Science Foundation of China for the financial support of this work. We also thank Prof. Xu, Jia-li for his contributions to this work.     

The use of a drug resistance cartridge for in vitro insertion and deletion mutagenesis of a cosmid clone

A drug-resistant cartridge was employed in the construction of families of insertion mutants of a cosmid clone. The cartridge contains a cml gene and has identical restriction enzyme sites, EcoRI, BamHI, SalI, and PstI, on both ends. The families of mutants were made by ligation of the cartridge to the cosmid, which was linearized or partially digested, followed by in vitro packaging and transduction. From these families we selected cosmid derivatives which either have a unique BamHI site at a predetermined site in the cosmid or have deletions covering different portions of the original clone. The extent of a large gene cluster cloned into the original cosmid was identified by confirming the gene function in some of the deletion mutants. The possibility for further and various uses of this cartridge is discussed.     

microRNA-1298 inhibits the malignant behaviors of breast cancer cells via targeting ADAM9

MicroRNAs (miRNAs) regulate the progression of human malignancy by targeting oncogenes or tumor suppressors, which are 12 promising targets for cancer treatment. Increasing evidence has suggested the aberrant expression and tumor-suppressive function of miR-1298 in cancers, however, the regulatory mechanism of miR-1298 in breast cancer (BC) remains unclear. Here, our findings showed that miR-1298 was down-regulated in BC tissues and cell lines. Lower level of miR-1298 was significantly correlated with the advanced progression of BC patients. Experimental study showed that overexpression of miR-1298 inhibited the proliferation, induced apoptosis and cell cycle arrest in BC cells. The in vivo xenograft mice model showed that highly expressed miR-1298 significantly reduced the tumor growth and metastasis. Further mechanism analysis revealed that miR-1298 bound the 3′-untranslated region (UTR) of a disintegrin and metalloproteinase 9 domain (ADAM9) and suppressed the expression of ADAM9 in BC cells. ADAM9 was overexpressed in BC tissues and inversely correlated with miR-1298. Down-regulation of ADAM9 induced apoptosis and cell cycle arrest of BC cells. Moreover, ectopic expression of ADAM9 by transiently transfecting with vector encoding the full coding sequence of ADAM9 attenuated the inhibitory effects of miR-1298 on the proliferation and cell cycle progression of BC cells. Collectively, our results illustrated that miR-1298 played a suppressive role in regulating the phenotype of BC cells through directly repressing ADAM9, suggesting the potential application of miR-1298 in the therapy of BC.     

Site-Specific Structural Variations Accompanying Tubular Assembly of the HIV-1 Capsid Protein

The 231-residue capsid (CA) protein of human immunodeficiency virus type 1 (HIV-1) spontaneously self-assembles into tubes with a hexagonal lattice that is believed to mimic the surface lattice of conical capsid cores within intact virions. We report the results of solid-state nuclear magnetic resonance (NMR) measurements on HIV-1 CA tubes that provide new information regarding changes in molecular structure that accompany CA self-assembly, local dynamics within CA tubes, and possible mechanisms for the generation of lattice curvature. This information is contained in site-specific assignments of signals in two- and three-dimensional solid-state NMR spectra, conformation-dependent ¹⁵N and ¹³C NMR chemical shifts, detection of highly dynamic residues under solution NMR conditions, measurements of local variations in transverse spin relaxation rates of amide ¹H nuclei, and quantitative measurements of site-specific ¹⁵N–¹⁵N dipole–dipole couplings. Our data show that most of the CA sequence is conformationally ordered and relatively rigid in tubular assemblies and that structures of the N-terminal domain (NTD) and the C-terminal domain (CTD) observed in solution are largely retained. However, specific segments, including the N-terminal β-hairpin, the cyclophilin A binding loop, the inter-domain linker, segments involved in intermolecular NTD–CTD interactions, and the C-terminal tail, have substantial static or dynamical disorder in tubular assemblies. Other segments, including the 3₁₀-helical segment in CTD, undergo clear conformational changes. Structural variations associated with curvature of the CA lattice appear to be localized in the inter-domain linker and intermolecular NTD–CTD interface, while structural variations within NTD hexamers, around local 3-fold symmetry axes, and in CTD–CTD dimerization interfaces are less significant.     

Small peptides,big roles ‒ RALFs regulate pollen tube growth and burst in plant reproduction

正In flowering plants,the pollen grain generates a pollen tube to deliver two immotile sperm cells to the embryo sac for double fertilization.After landing on the stigma of the pistil,the pollen grain hydrates and germinates to produce a pollen tube,which penetrates the style and grows into the transmitting tract.The pollen tube then emerges onto the surface of the septum,grows along the funiculus,responds to the attraction signals from the synergid cells of the embryo sac and targets the ovule micropyle.     

Parasitism ofAphis gossypii (Homoptera: Aphididae) byAllothrombium pulvinum larvae (Acari: Trombidiidae) in cotton fields: spatial dispersion and density dependence

Spatial aspects of the interaction between the aphid host,Aphis gossypii, and its parasite,Allo-thrombium pulvinum larvae, on cotton plants were examined in seven fields in China. For both the host and the parasite, sample variance increased with the mean according to Taylor's power law, which explained a substantial proportion (84–97%) of the variation in the data. Although both the host and parasite showed aggregated distribution on cotton plants, the host aphids aggregated more strongly than the parasites. The host dispersion pattern was not significantly affected by the presence of parasites. Increasing the spatial scales of observation from individual plot to the entire field also had no significant effects on host and parasite dispersion patterns. Parasites aggregated in cotton plants with higher aphid densities in five out of the seventeen samples. Spatial patterns of parasitism were mostly host density-independent (71% of the samples) and sometimes inversely density-dependent (29% of the sample). The processes underlying these patterns were discussed.