Fast-response fluorescent probe with favorable water solubility for highly sensitive imaging of endogenous tyrosinase in living cells and zebrafish model

Tyrosinase(TYR) is an important polyphenolic oxidase enzyme and usually regards as a biomarker of melano ma cancer.Highly effective tracking TYR activity in vivo will help to study the mechanism of TYR in living organisms and forecasts related diseases.In this study,we present a novel TYR-activatable fluo rescent probe(CHMC-DOPA) for tracking TYR activity in vitro and in vivo.CHMC-DOPA is constructed by incorporating dopamine(DOPA) moiety into a fluorescent chloro-hydroxyl-merocyanine(CHMC)scaffold.Upon exposure to TYR,the dopamine unit in CHMC-DOPA is oxidized to a dopaquinone derivative,and an intramolecular photo-induced electron transfer(PET) process between CHMC fluorophore and o-dopaquinone will take place,the fluorescence of CHMC-DOPA is quenched rapidly.Therefore,the evaluation of TYR activity is established in terms of the relationship between fluorescence quenching efficiency and TYR activity.In our experiments,CHMC-DOPA shows various advantages,such as fast response(8 min),low concentration of TYR activation(0.5 U/mL),good water-solubility,as well as the lowest detection limit(0.003 U/mL) compared with previously reported works.Furthermore,CHMCDO PA also exhibits excellent cell membrane permeability and low cytotoxicity,which is successfully used to monitor endogenous TYR activity in living cancer cells and zebrafish models.CHMC-DOPA performs well,and we anticipate that this newly designed novel platform will provide an alternative for high effective monitoring TYR activity in biosystems.

Fast Optical Switching Using Oriented Cyanine Dye-Doped Nematic Liquid Crystal

A cyanine dye, 2-[7-（1,3-dihydro-1,3,3-trimethyl-2H-indol-2-ylidene）-1,3,5-heptatrienyl]-1,3,3-trimethyl-3H-indolium iodide （NK-125）, is doped in 4-cyano-4＇-pentylbiphenyl （5 CB）, and the mixture is sandwiched between two pieces of rubbed glass plates. The third-order nonlinear optical properties of the oriented NK-125-SCB layers are measured by the resonant femtosecond degenerate four-wave mixing （DFWM） technique at 760 nm. The third-order nonlinear optical susceptibility of one of the present samples is 5.5×10^-8 esu. The slow DFWM response of the NK-125-SCB layers due to a population grating is accelerated by the increasing laser power because of amplified spontaneous emission （ASE）. On the other hand, we do not observe a similar phenomenon for NK-125- polyethylene glycol （PEG-400）. Oriented NK-125 molecules in nematic liquid crystals must have very high ASE efficiency. Hence the population grating in a DFWM signal disappears within about 4 ps. It is expected that NK-125-SCB can be used as a material for very fast all-optical switching.

Monolithic quasi-sliding-mode controller for SIDO buck converter with a self-adaptive free-wheeling current level

An analog implementation of a novel fixed-frequency quasi-sliding-mode controller for single-inductor dual-output（SIDO） buck converter in pseudo-continuous conduction mode（PCCM） with a self-adaptive freewheeling current level（SFCL） is presented.Both small and large signal variations around the operation point are considered to achieve better transient response so as to reduce the cross-regulation of this SIDO buck converter.Moreover,an internal integral loop is added to suppress the steady-state regulation error introduced by conventional PWM-based sliding mode controllers.Instead of keeping it as a constant value,the free-wheeling current level varies according to the load condition to maintain high power efficiency and less cross-regulation at the same time.To verify the feasibility of the proposed controller,an SIDO buck converter with two regulated output voltages,1.8 V and 3.3 V,is designed and fabricated in HEJIAN 0.35 m CMOS process.Simulation and experiment results show that the transient time of this SIDO buck converter drops to 10 s while the cross-regulation is reduced to 0.057 mV/mA,when its first load changes from 50 to 100 mA.