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Hydroxylated derivatives of steroids play essential roles in medicine. Cytochrome P450 enzymes selectively hydroxylate methyne groups on steroids, which can dramatically change their polarity, biological activity and toxicity.

Cytochrome P450 enzymes (CYPs or P450s) are ubiquitous heme-dependent enzymes that catalyze the monooxygenation of non-activated C-H bonds to modify the structure of the substrate. In this study, we heterologously expressed CYP107X1 from Streptomyces avermitilis and conducted in vitro substrate screening using the alternative redox partners putidaredoxin and putidaredoxin reductase. CYP107X1 catalyzed the 16α-hydroxylation of progesterone with regio- and stereoselectivity. The spectroscopic analyses showed that CYP107X1 bound progesterone with a relatively high K

Stimulated Brillouin scattering (SBS), as one type of third-order nonlinear optics effect, is extensively exploited and rapidly developed in the field of lasers and optoelectronics. A large number of theoretical and experimental studies on SBS have been carried out in the past decades. Especially, the exploration of new SBS materials and new types of SBS modulation methods have been engaged simultaneously, as the properties of different materials have great influence on the SBS performance such as generation threshold, Brillouin amplification efficiency, frequency shift, breakdown threshold, etc. This article provides a comprehensive review of the characteristics of different types of SBS materials, SBS applications, experimental design methods, as well as the parameter optimization method, which is expected to provide reference and guidance to SBS related experiments.

A novel approach of beam cleanup based on stimulated Brillouin scattering with a large core fiber is proposed to improve the laser beam quality. The fusion splice scheme from a single-mode fiber to a very large core fiber (105 µm) is first employed in stimulated Brillouin scattering to steadily excite the fundamental mode of the Stokes beam. As a result, the output beam achieves a measured M2 value of around 1.3 meanwhile the pump conversion efficiency is up to 90%, which is the best in the reports of stimulated Brillouin scattering cleanup to our knowledge.

Stimulated Brillouin Scattering in multimode fiber leads to the event of beam cleanup, which has attractive potential applications in improving the beam quality of multimode fiber laser with large core diameter and high peak power. We report the experimental setup and result that using Stimulated Brillouin Scattering in 105μm core diameter GI fiber to achieve beam cleanup when the 20kW peak power pulsed pump is provided, and getting a high-quality output with M2≈1.5.

We demonstrate an novel intensity based demodulation scheme for FBG sensors. The wavelength shifts of FBG sensors are transferred to the light power changes by a demodulator based on the multimode interference of multimode fiber. A demonstration system is built up, based on a broadband source ASE, a photo detector, and a ~5cm long step-index multimode fiber with core/cladding radius 52.5/62.5≠m is used. The static and dynamic tests of the sensing system are given to prove the feasibility of the intensity based demodulator.

The conditions leading to the beam cleanup effect induced by stimulated Brillouin scattering (SBS) have been debated by many researchers. In this paper, we firstly reveal that the key point of the beam cleanup induced by SBS is at the selective excitation of the fundamental mode of the Stokes beam, which is amplified by the counterpropagating high-order-mode pump beam along multimode fibers while preserving the fundamental mode and subsequently realizing the beam cleanup. This mechanism is theoretically modeled and experimentally demonstrated in this work.