Expression and characterization of a novel halohydrin dehalogenase from Rhodospirillaceae bacterium / 生物工程学报

As a class of multifunctional biocatalysts, halohydrin dehalogenases are of great interest for the synthesis of chiral β-substituted alcohols and epoxides. There are less than 40 halohydrin dehalogenases with relatively clear catalytic functions, and most of them do not meet the requirements of scientific research and practical applications. Therefore, it is of great significance to excavate and identify more halohydrin dehalogenases. In the present study, a putative halohydrin dehalogenase (HHDH-Ra) from Rhodospirillaceae bacterium was expressed and its enzymatic properties were investigated. The HHDH-Ra gene was cloned into the expression host Escherichia coli BL21(DE3) and the target protein was shown to be soluble. Substrate specificity studies showed that HHDH-Ra possesses excellent specificity for 1,3-dichloro-2-propanol (1,3-DCP) and ethyl-4-chloro-3-hydroxybutyrate (CHBE). The optimum pH and temperature for HHDH-Ra with 1,3-DCP as the reaction substrate were 8.0 and 30 °C, respectively. HHDH-Ra was stable at pH 6.0-8.0 and maintained about 70% of its original activity after 100 h of treatment. The thermal stability results revealed that HHDH-Ra has a half-life of 60 h at 30 °C and 40 °C. When the temperature is increased to 50 °C, the enzyme still has a half-life of 20 h, which is much higher than that of the reported enzymes. To sum up, the novel halohydrin dehalogenase from Rhodospirillaceae bacterium possesses good temperature and pH stability as well as catalytic activity, and shows the potential to be used in the synthesis of chemical and pharmaceutical intermediates.

Comparative study of multi-slice spiral computed tomography angiography with DSA in lower extremity arteriosclerosis obliterans / 实用放射学杂志

Objective To discuss the value of multi-slice spiral CT angiography (MSCTA)and digital subtraction angiography (DSA)in lower extremity arteriosclerosis obliterans.Methods MSCTA and DSA of lower extremity arteries were performed in 41 patients with lower extremity arteriosclerosis obliterans sequentially.The interval of these two examinations was no more than 2 weeks.DSA served as the reference standard and compared with MSCTA in terms of grading of stenoocclusive lesions,visualization of collaterals in lower extremity arteries.Results No significant differences of grading of stenoocclusive lesions,visualization of col-laterals were observed between MCTA and DSA in lower extremity arteries.Compared with the results of DSA,the sensitivity,spe-cificity,accuracy,positive and negative predictive value of MSCTA in the detection of arterial stenosis (≥ 50%)were 97.2%, 98.2%,93.8%,94.6%,98.2%,respectively.Conclusion MSCTA shows relatively high sensitivity and specificity in the diagnosis of lower extremity arteriosclerosis obliterans,can provide effective guidance of planning treatment in lower extremity arteriosclerosis obliterans.