Reduced salinity interacts with ultraviolet radiation to alter photosystem Ⅱ function in diatom Skeletonema costatum

To investigate the effect of reduced salinity on diatoms’ capacity to cope with changing ultraviolet radiation(U VR) and photosynthetically active radiation(PAR),Skeletonema costatum was grown in a range of salinity(15,25,and 35).The photo system Ⅱ(PSⅡ) function was analyzed by increasing PAR and UVR to mimic a mixing event in turbulent waters.The re sults show that high UVR exposure significantly reduced PSII activity,especially in cells grown at low salinity.UVR,but not salinity,stimulated the ’removal’ rate of PSII protein PsbA.Salinity alone,in the range of 15 to 35,did not regulate PSⅡ acceptor region;however,the low salinity+UVR treatment decreased the energy flux for electron transport per PSⅡ reaction center in S.costatum.It showed that low salinity exacerbated the damaging effect of UVR on PSⅡ function in S.costatum by suppressing Psb A protein synthe sis and modifying the photochemistry of PSⅡ.Although higher catalase(CAT) activity and NPQs were induced,they were unable to prevent the combined damage effect of low salinity+UVR.Our findings indicate that reduced salinity and increased UVR potentially affect the abundance and distribution of S.costatum with the escalation of climate disturbances.

Separation and identification of the major components of Photocarcinorin and their tumor-photobiological activities

It has been shown by the results-of HPLC analysis in combination with spectrographicdeterminations that PsD-007 is composed of 7 different porphyrins,In order of the proportion inPsD-007,they are:3 （or 8）-（l-methoxyethyl）-8 （or 3）-（l-hydroxyethyl）-deuteroporphyrin Ⅸ（MHD）;3,8-di-（l-methoxyethyl）-deuteroporphyrin Ⅸ（DMD）;3（or 8）-（l-methoxyethyl）-8 （or3）-vinyl-deuteroporphyrin Ⅸ（MVD）;3（or 8）-（l-hydroxyethyl）-8（or 3）-vinyl-deuteroporphyrin Ⅸ（HVD）;hernatoporphyrin Ⅸ （Hp）;protoporphyrin Ⅸ （Pp） and 3（or 8）-（O-aceylethyl）-8（or 3）-（l-hydroxyethyl）-deuteroporphrin Ⅸ （AHD）,which presented only in crude PsD-007 and hasbeen transformed into MHD and Hp,respectively during the separation and preparing the clinicalpreparation of PsD-007.Structures of these porphyrins were further eonfirmed by the corre-sponding anthentic samples obtained by synthetic method.It was found on the basis of the experi-mental data of photosensitizing ability in cell-free systems and photoinactivation of human cancercells in vitro as well as efficacy of photodynamic therapy for sarcoma.S180 in mice of the ma-jor components MILD,DMD and MVD composed of which more over 85% of the totalamount of PsD-007,that they all exhibited comparatively high photosensitizing ability andphotodynamic effects on cancer cells and tram-planted animal tumor.

Possible therapeutic targets and promising drugs based on unsymmetrical hetaryl-substituted porphyrins to combat SARS-CoV-2

Coronavirus disease 2019 is a serious disease that causes acute respiratory syndrome and negatively affects the central nervous system.Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)crosses the blood-brain barrier due to the spike(S) protein on the surface of the viral particles.Thus,it is important to develop compounds that not only have an inhibitory effect but are also capable of completely deactivating the S protein function.This study describes the purposeful modification of porphyrins and proposes compounds,asymmetrically hetaryl-substituted porphyrins with benzothiazole,benzoxazole,and N-methylbenzimidazole residues,to deactivate the S protein functions.Molecular docking of SARS-CoV-2 proteins with hetaryl-substituted porphyrins showed that the viral S protein,nucleocapsid(N) protein,and non-structural protein 13(nsp13) exhibited the highest binding affinity.Hetaryl-substituted porphyrins form strong complexes(13-14 kcal/mol) with the receptor-binding domain of the S protein,while the distance from the porphyrins to the receptor-binding motif(RBM)does not exceed 20 ?;therefore,RBM can be oxidized by ^(1)O_(2),which is generated by porphyrin.Hetarylsubstituted porphyrins interact with the N protein in the serine/arginine-rich region,and a number of vulnerable amino acid residues are located in the photooxidation zone.This damage complicates the packaging of viral RNA into new virions.High-energy binding of hetaryl-substituted porphyrins with the N-and C-terminal domains of nsp13 was observed.This binding blocks the action of nsp13 as an enzyme of exoribonuclease and methyltransferase,thereby preventing RNA replication and processing.A procedure for the synthesis of hetaryl-substituted porphyrins was developed,new compounds were obtained,their structures were identified,and their photocatalytic properties were studied.