Construction and optimization of squalene epoxide synthetic pathway in Escherichia coli / 生物工程学报

Triterpenoids are a class of natural products of great commercial value that are widely used in pharmaceutical, health care and cosmetic industries. The biosynthesis of triterpenoids relies on the efficient synthesis of squalene epoxide, which is synthesized from the NADPH dependent oxidation of squalene catalyzed by squalene epoxidase. We screened squalene epoxidases derived from different species, and found the truncated squalene epoxidase from Rattus norvegicus (RnSETC) showed the highest activity in engineered Escherichia coli. Further examination of the effect of endogenous cytochrome P450 reductase like (CPRL) proteins showed that overexpression of NADH: quinone oxidoreductase (WrbA) under Lac promoter in a medium-copy number plasmid increased the production of squalene epoxide by nearly 2.5 folds. These results demonstrated that the constructed pathway led to the production of squalene epoxide, an important precursor for the biosynthesis of triterpenoids.

Repeatability and reproducibility of macular thickness profiles of intra-retinal layers determined by an automated algorithm with RTVue100 OCT / 中华实验眼科杂志

Background Evaluation of intra-retinal layer thickness plays an important role in the diagnosis and monitor of various eye diseases,and spectral domain optical coherence tomography (OCT) is a frequently used tool.Software analysis method was used to measure the retinal thickness in previous study,but the study on the reliability of automatic layered software is lack.Objective This study was to evaluate the repeatability and reproducibility of thickness profile measurement of intra-retinal layers determined by an automated algorithm applied to OCT images from RTVue100 OCT instrument.Methods In this prospective cross-sectional study,retinal thickness images at 6 mm around fovea were obtained from 18 right eyes of 18 normal subjects with RTVue100 OCT instrument.The retinal images were segmented into retinal nerve fiber layer (RNFL),ganglion cell layer and inner plexiform layer(GCL+IPL),inner nuclear layer (INL),outer plexiform layer (OPL),outer nuclear layer (ONL),inner segment (IS),outer segment (OS) and retinal pigment epithelial (RPE) layer using automated algorithm method.Then Matlab software was used to analyze the measuring outcome.Interclass correlation coefficient (ICC) and coefficients of reproducibility (COR) were calculated from the results of two-time examination by the same examiner to evaluate the repeatability and from the results of two different examiners to assess the reproducibility.Written informed consent was obtained from each subject prior to any medical procedure.Results The entire retinal thickness measured by RTVue-OCT was (303.22± 14.10) μm in the horizontal meridian and (306.68 ± 13.32) μm in the vertical meridian,with the maximum values of retinal thickness in the GCL+ IPL and ONL.Whether in the horizontal meridian or in the vertical meridian,the ICC and COR were ＜0.60 in the OPL,IS and OS;while those in the RNFL,GCL+IPL,INL,ONL and RPE layer were ＞0.70.Conclusions RTVue OCT with automated algorithm is a useful and reliable approach to the measurement of intra-retinal layer thickness.Automated segmentation can offer accurate and repeatable thickness profile of OCT retinal image.This method may improve the diagnosis and monitoring of retinal diseases.