Gas Phase Hydrogenated and Deuterated Fullerene Cations

H/D accretion,especially onto ionized fullerenes,is expected to be very efficient in space.In this work,we study hydrogenated and deuterated fullerene cations and their photodissociation behavior in the gas phase.The experimental results show that hydrogenated fullerene cations(i.e.,[C_(60)H_(n)]^(+)and[C_(70)H_(n)]^(+),n up to 30)and deuterated fullerene cations(i.e.,[C_(60)D_(n)]^(+)and[C_(70)D_(n)]^(+),n up to 21)are formed efficiently through the ion-atom collision reaction pathway.Upon irradiation,the hydrogenated and deuterated fullerene cations dissociate into fullerene cations and H/H_(2)or D/D_(2)species.The structures of the newly formed hydrogenated and deuterated fullerene cations(C_(58)and C_(60))and the bonding energies for these reaction pathways are investigated by means of quantum chemical calculations.The competition between hydrogenation and dehydrogenation is confirmed,and the hydrogenation-to-dehydrogenation ratio in the accretion processes in the gas phase is determined.We infer that the proportion of accreted hydrogen and deuterium atoms on the surface of fullerenes is similar to that of hydrogen and deuterium atoms in the interstellar environment where these fullerenes are located,especially when the interstellar environments are similar to our experimental conditions,i.e.,the hot environment.

Constraints on water activity at the Zhurong landing site in Utopia Planitia,Mars

Mineralogical evidence of water–rock interactions is a strong indicator of the presence of liquid water on ancient Mars.Previous observations have found widely distributed hydrated minerals in the southern highlands,whereas such discoveries have been rare in the younger northern lowlands.China’s first Mars exploration mission successfully landed a rover(Zhurong)in southern Utopia Planitia,providing an opportunity to analyze the exposed rocks in the northern lowlands.Using data from the short-wave infrared(SWIR)spectrometer and the laser-induced breakdown spectrometer(LIBS)onboard the Zhurong rover,we found evidence for the widespread presence of hydrated minerals(probably sulfates or silica)around the landing site.The basaltic-like elemental compositions of the targeted samples further indicated that hydrated minerals are likely minor components.The results from Zhurong suggest that active aqueous activities occurred during the overall cold and dry Amazonian era on Mars.However,further evaluations are needed on the duration and scale of these activities.

Protein post-translational modification by lysine succinylation:Biochemistry,biological implications,and therapeutic opportunities

Lysine succinylation(Ksuc)is a novel protein post-translational modification(PTM)wherein a succinyl group modifies a lysine residue.Ksuc leads to significant chemical and struc-tural changes to the modified protein.Recent studies have shown that Ksuc might play an important role in organism physiology and some pathophysiological processes,such as tumor-igenesis and metabolic diseases.To provide an understanding of the molecular mechanism and functions of Ksuc in different organisms,we reviewed the current literature about Ksuc,mainly summarizing the research advances in eukaryotes and prokaryotes based on both traditional study methods and site prediction tools.We also discussed inhibitors or activators associated with Ksuc that may contribute to proteomic studies and could be useful in future clinical prac-tice.A deeper understanding of Ksuc may shed new light on life science at the protein level and could lead to novel therapeutic strategies for various diseases.

Mycobacterium Lrp/AsnC family transcriptional factor modulates the arginase pathway as both a sensor and a transcriptional repressor

L-Arginine is the precursor of nitric oxide(NO),a host immune effector against intracellular pathogens including Mycobacterium tuberculosis(M.tb).Pathogens including M.tb have evolved various strategies targeting arginine to block the production of NO for better survival and proliferation.However,L-arginine metabolism and regulation in Mycobacterium are poorly understood.Here,we report the identification of M.smegmatis MSMEG_1415(homolog of M.tb Rv2324)as an arginine-responsive transcriptional factor regulating the arginase pathway.In the absence of L-arginine,MSMEG_1415 acts as a repressor to inhibit the transcription of the roc(for arginine,ornithine catabolism)gene cluster,thereby switching off the arginase pathway.Treatment with L-arginine relieves the transcriptional inhibition of MSMEG_1415 on the roc gene cluster to activate the arginase pathway.Moreover,the L-arginine-MSMEG_1415 complex activates the transcription of the roc gene cluster by recognizing and binding a 15-bp palindrome motif,thereby preventing the excess accumulation of L-arginine in M.smegmatis.Physiologically,MSMEG_1415 confers mycobacteria resistance to starvation and fluoroquinolones exposure,suggestive of its important role in M.smegmatis persistence.The results uncover a unique regulatory mechanism of arginine metabolism in mycobacteria and identify M.tb Rv2324 as an attractive candidate target for the design of drugs against tuberculosis.