The mechanical stability of tRNAs contributes to their biological activities.The mitochondrial tRNAArg from Romanomermis culicivorax is the shortest tRNA ever known.This tRNA lacks D-and T-arms,represents a stem-bulge...The mechanical stability of tRNAs contributes to their biological activities.The mitochondrial tRNAArg from Romanomermis culicivorax is the shortest tRNA ever known.This tRNA lacks D-and T-arms,represents a stem-bulge-stem architecture but still folds into a stable tertiary structure.Although its structure had been reported,studies on its mechanical folding and unfolding kinetic characteristics are lacking.Here,we directly measured the single-molecule mechanical folding and unfolding kinetics of the armless mt tRNAArg by using optical tweezers in different solution conditions.We revealed a two-step reversible unfolding pathway:the first and large transition corresponds to the unfolding of acceptor stem and bulge below 11 pN,and the second and small transition corresponds to the unfolding of anticodon arm at 12 pN-14 pN.Moreover,the free energy landscapes of the unfolding pathways were reconstructed.We also demonstrated that amino acid-chelated Mg^(2+)(aaCM),which mimics the intracellular solution condition,stabilizes the bulge of mitochondrial tRNAArg possibly by reducing the topological constraints or stabilizing the possible local non-canonical base pairings within the bulge region.Our study revealed the solution-dependent mechanical stability of an armless mt tRNA,which may shed light on future mt tRNA studies.展开更多
Precise determination of oxygen concentrations is vital in a wide range of applications.Molecules with balanced phosphorescence and fluorescence can act as ratiometric oxygen sensors,and these singlemolecule sensors r...Precise determination of oxygen concentrations is vital in a wide range of applications.Molecules with balanced phosphorescence and fluorescence can act as ratiometric oxygen sensors,and these singlemolecule sensors represent the most accurate approach for oxygen sensing.Harnessing the different degrees of singlet–triplet state mixing induced by different lanthanides,a double-ring porphyrin(sinoporphyrin sodium,DVDMS)was simultaneously coordinated to gadolinium(Ⅲ)and praseodymium(Ⅲ)to balance the excited-state populations.The fluorescence and phosphorescence quantum yields for this lanthanide complex(PrGd-DVDMS)were 0.17%and 0.66%,respectively.Thus,the phosphorescence-tofluorescence intensity ratio of PrGd-DVDMS was only 3:1;this compares very favorably with that for DVDMS coordinated to two gadolinium(Ⅲ)ions(Gd_(2)-DVDMS),which was 30:1.Furthermore,PrGd-DVDMS displayed excellent ratiometric oxygen sensing characteristics,and the uncertainty in its phosphorescence-to-fluorescence intensity ratio was considerably lower than that of Gd_(2)-DVDMS.This new mixed-lanthanide porphyrin therefore has excellent potential as an oxygen indicator for applications such as environmental monitoring that require high reliability.展开更多
We present a general relationship between the magnetisation blocking temperature(T_(B))measured using the zero-field cooling/field cooling technique(ZFC/FC)and the temperature-dependent spin relaxation time obtained f...We present a general relationship between the magnetisation blocking temperature(T_(B))measured using the zero-field cooling/field cooling technique(ZFC/FC)and the temperature-dependent spin relaxation time obtained from AC susceptibility and magnetisation decay measurements.The presented mathematical approach supplies ZFC/FC blocking temperatures at any heating rate(R_(H)),providing comparable values to those obtained experimentally,as demonstrated by testing 107 examples for reported singlemolecule magnets(SMMs)where the ZFC/FC curve has been measured.This procedure is examined in further detail for a new single-molecule magnet,[Dy(OPAd_(2)Bz)_(2)(H_(2)O)4Br]Br_(2)·4THF(1)(OPAd_(2)Bz:di(1-adamantyl)benzylphosphine oxide).For this compound,ZFC/FC measurements were made over a broad range of heating rates(0.01-5 K min^(−1)),which agreed with the general behaviour predicted from AC susceptibility data.We discuss how the demagnetisation mechanism determines the sensitivity of T_(B)with respect to the heating rate:T_(B)is mostly insensitive to R_(H)for Orbach relaxation,while there is a larger sensitivity for Raman-limited systems.Our conclusions provide a clear physical interpretation of ZFC/FC blocking temperatures,aiding in the proper contextualization of this figure of merit.展开更多
Light-induced transformation from diamagnetic ligand to paramagnetic radical offers a unique approach to modulating the magnetization dynamics of magnetic compounds.In this study,we present a two-dimensional Yb(III)co...Light-induced transformation from diamagnetic ligand to paramagnetic radical offers a unique approach to modulating the magnetization dynamics of magnetic compounds.In this study,we present a two-dimensional Yb(III)coordination polymer 1 and its Y(III)-diluted analog 1@Y,along with their lightinduced radical forms,1a and 1a@Y.Due to the presence of light-induced radicals,the magnetic susceptibility properties(_(χM)T values)of 1a and 1a@Y featured remarkable 82.3%and 88.9%enhancements,respectively,at room temperature,compared with those of 1 and 1@Y,and were accompanied by an unexpected increase in the effective energy barrier for magnetization dynamics.The magnetization dynamics of 1 and 1a involved both Orbach and Raman processes,while 1@Y and 1a@Y exhibited two Raman processes,indicating that the Orbach process that occurred in 1 and 1a was mainly attributed to the magnetic coupling between Yb(III)ions.This work showcases the potential of light-induced radical transformation for tuning both the static and dynamic magnetic properties of lanthanide coordination polymers.展开更多
Molecular machines transduce energy from one form to another through controlled motion in response to stimuli.Despite the ubiquitous use of molecular machines in biology,understanding the detailed mechanisms of such c...Molecular machines transduce energy from one form to another through controlled motion in response to stimuli.Despite the ubiquitous use of molecular machines in biology,understanding the detailed mechanisms of such complex structures remains challenging.Recent progress in studying the modes of operation of synthetic small-molecule machines at the single-molecule level has shed new light on the mechanisms of nano-machinery.In this mini-review,we focus on the study of artificial small-molecule machines using single-molecule techniques,including single-molecule force spectroscopy,single-molecule electrical spectroscopy,and single-molecule optical spectroscopy.We survey the techniques used to monitor single-molecule behavior to date and describe the latest studies on small-molecule machines,highlighting their common features and challenges that need to be overcome to realize the potential of these techniques in unraveling the behavior of small molecule systems.展开更多
Van der Waals(vdW)contact,dominated by weak but ubiquitous vdW interactions,plays a significant role in diverse fields such as supramolecular chemistry,nanotechnology,and surface science.Accurate characterization of v...Van der Waals(vdW)contact,dominated by weak but ubiquitous vdW interactions,plays a significant role in diverse fields such as supramolecular chemistry,nanotechnology,and surface science.Accurate characterization of vdW contact at the single-molecule level remains challenging.Herein,we combine the scanning tunneling microscope break junction technique with first-principles calculations to study the mechanical and electrical characteristics of the alkane/Au vdW contact in an in-situ solution environment.The step-like conductance plateaus indicate a gradual desorption of alkyl chains in units of two methylene groups under force stretching.Two distinct charge transport channels,through the shortest C–H/Au pathway and the entire adsorbed alkyl chain,are identified.Furthermore,we discover that a higher electric field leads to increased conductance and stronger bonding of the alkane/Au vdW contact.These results unveil the intrinsic properties of vdW contact at the molecular and even atomic levels,which are crucial for exploring noncovalent interactions and advancing molecular sciences.展开更多
基金supported by the Natural Science Foundation of Guangdong Province,China(Grant No.2017A030310085)the Science and Technology Planning Project of Guangdong Province,China(Grant No.2018A050506034).
文摘The mechanical stability of tRNAs contributes to their biological activities.The mitochondrial tRNAArg from Romanomermis culicivorax is the shortest tRNA ever known.This tRNA lacks D-and T-arms,represents a stem-bulge-stem architecture but still folds into a stable tertiary structure.Although its structure had been reported,studies on its mechanical folding and unfolding kinetic characteristics are lacking.Here,we directly measured the single-molecule mechanical folding and unfolding kinetics of the armless mt tRNAArg by using optical tweezers in different solution conditions.We revealed a two-step reversible unfolding pathway:the first and large transition corresponds to the unfolding of acceptor stem and bulge below 11 pN,and the second and small transition corresponds to the unfolding of anticodon arm at 12 pN-14 pN.Moreover,the free energy landscapes of the unfolding pathways were reconstructed.We also demonstrated that amino acid-chelated Mg^(2+)(aaCM),which mimics the intracellular solution condition,stabilizes the bulge of mitochondrial tRNAArg possibly by reducing the topological constraints or stabilizing the possible local non-canonical base pairings within the bulge region.Our study revealed the solution-dependent mechanical stability of an armless mt tRNA,which may shed light on future mt tRNA studies.
基金supported by the National Natural Science Foundation of China(grant numbers 61905132,61805128,82102052)the China Postdoctoral Science Foundation(grant number 2019M662425).
文摘Precise determination of oxygen concentrations is vital in a wide range of applications.Molecules with balanced phosphorescence and fluorescence can act as ratiometric oxygen sensors,and these singlemolecule sensors represent the most accurate approach for oxygen sensing.Harnessing the different degrees of singlet–triplet state mixing induced by different lanthanides,a double-ring porphyrin(sinoporphyrin sodium,DVDMS)was simultaneously coordinated to gadolinium(Ⅲ)and praseodymium(Ⅲ)to balance the excited-state populations.The fluorescence and phosphorescence quantum yields for this lanthanide complex(PrGd-DVDMS)were 0.17%and 0.66%,respectively.Thus,the phosphorescence-tofluorescence intensity ratio of PrGd-DVDMS was only 3:1;this compares very favorably with that for DVDMS coordinated to two gadolinium(Ⅲ)ions(Gd_(2)-DVDMS),which was 30:1.Furthermore,PrGd-DVDMS displayed excellent ratiometric oxygen sensing characteristics,and the uncertainty in its phosphorescence-to-fluorescence intensity ratio was considerably lower than that of Gd_(2)-DVDMS.This new mixed-lanthanide porphyrin therefore has excellent potential as an oxygen indicator for applications such as environmental monitoring that require high reliability.
基金FONDECYT Regular 1210325 for financial support.Powered@NLHPC:this research was partially supported by the supercomputing infrastructure of the NLHPC(ECM-02)Financial support from the Ministerio de Ciencia e Innovación(projects PID2022-138090NB-C21,PID2021-122464NB-I00,TED2021-129593B-I00,CNS2023-144561 and Maria de Maeztu CEX2021-001202-M)+5 种基金the Junta de Andalucía(FQM-195 and FQM-337)FEDER/Junta de Andalucía(projects I+D+i P20_00692,C-EXP-140-UGR23 and M.1.B.B TA_000722,Programas Operativos FEDER 2014-2020 y 2021-2027,Consejería de Economía,Conocimiento,Empresas y Universidad)the University of Granada(project I+D+i PPJIA2020.10)is greatly appreciatedthe Centro de Servicios de Informática y Redes de Comunicaciones(CSIRC)for computational time and facilitiesthe Ministerio de Ciencia e Innovación for a Ramón y Cajal contract(the publication is part of the project PID2022-138090NB-C21 and grant RYC2021-034288-I funded by MCIN/AEI/10.13039/501100011033 and by the European Union“NextGenerationEU”/PRTR”)the Generalitat de Catalunya for ICREA Academia and 2021-SGR-00286 grants,and for computational resources at CSUC.
文摘We present a general relationship between the magnetisation blocking temperature(T_(B))measured using the zero-field cooling/field cooling technique(ZFC/FC)and the temperature-dependent spin relaxation time obtained from AC susceptibility and magnetisation decay measurements.The presented mathematical approach supplies ZFC/FC blocking temperatures at any heating rate(R_(H)),providing comparable values to those obtained experimentally,as demonstrated by testing 107 examples for reported singlemolecule magnets(SMMs)where the ZFC/FC curve has been measured.This procedure is examined in further detail for a new single-molecule magnet,[Dy(OPAd_(2)Bz)_(2)(H_(2)O)4Br]Br_(2)·4THF(1)(OPAd_(2)Bz:di(1-adamantyl)benzylphosphine oxide).For this compound,ZFC/FC measurements were made over a broad range of heating rates(0.01-5 K min^(−1)),which agreed with the general behaviour predicted from AC susceptibility data.We discuss how the demagnetisation mechanism determines the sensitivity of T_(B)with respect to the heating rate:T_(B)is mostly insensitive to R_(H)for Orbach relaxation,while there is a larger sensitivity for Raman-limited systems.Our conclusions provide a clear physical interpretation of ZFC/FC blocking temperatures,aiding in the proper contextualization of this figure of merit.
基金supported by the National Natural Science Foundation of China(grant nos.22435002a,92156002,21971123,and 62401563)L.U.acknowledges the financial support of the research projects A-800079-00-00,A-8000017-00-00,and A-8001894-00-00 of the National University of Singapore(NUS)+1 种基金Ab initio calculations were done on the Advanced Supercomputer for Petascale Innovation,Research and Enterprise 2A(ASPIRE-2A)cluster of the Singapore National Supercomputing Centre(NSCCwww.nscc.sg)under project 11001278.The highperformance computational(HPC)resources of NUS(HPC-NUS)are gratefully acknowledged.The NUS Research Scholarship program supported W.H.
文摘Light-induced transformation from diamagnetic ligand to paramagnetic radical offers a unique approach to modulating the magnetization dynamics of magnetic compounds.In this study,we present a two-dimensional Yb(III)coordination polymer 1 and its Y(III)-diluted analog 1@Y,along with their lightinduced radical forms,1a and 1a@Y.Due to the presence of light-induced radicals,the magnetic susceptibility properties(_(χM)T values)of 1a and 1a@Y featured remarkable 82.3%and 88.9%enhancements,respectively,at room temperature,compared with those of 1 and 1@Y,and were accompanied by an unexpected increase in the effective energy barrier for magnetization dynamics.The magnetization dynamics of 1 and 1a involved both Orbach and Raman processes,while 1@Y and 1a@Y exhibited two Raman processes,indicating that the Orbach process that occurred in 1 and 1a was mainly attributed to the magnetic coupling between Yb(III)ions.This work showcases the potential of light-induced radical transformation for tuning both the static and dynamic magnetic properties of lanthanide coordination polymers.
基金supported the National Natural Science Foundation of China(grant no.22001074 to L.Z.)the Natural Science Foundation of Shanghai(grant no.22ZR1479400 to L.Z.).
文摘Molecular machines transduce energy from one form to another through controlled motion in response to stimuli.Despite the ubiquitous use of molecular machines in biology,understanding the detailed mechanisms of such complex structures remains challenging.Recent progress in studying the modes of operation of synthetic small-molecule machines at the single-molecule level has shed new light on the mechanisms of nano-machinery.In this mini-review,we focus on the study of artificial small-molecule machines using single-molecule techniques,including single-molecule force spectroscopy,single-molecule electrical spectroscopy,and single-molecule optical spectroscopy.We survey the techniques used to monitor single-molecule behavior to date and describe the latest studies on small-molecule machines,highlighting their common features and challenges that need to be overcome to realize the potential of these techniques in unraveling the behavior of small molecule systems.
基金financial support from the National Key R&D Program of China(grant nos.2021YFA1200102,2021YFA1200101,and 2022YFE0128700)the National Natural Science Foundation of China(grant nos.22173050,22150013,21727806,21933001,and 11974106)+3 种基金the New Cornerstone Science Foundation through the XPLORER PRIZE,the Natural Science Foundation of Beijing(grant no.2222009)Beijing National Laboratory for Molecular Sciences(grant no.BNLMS202105)the Fundamental Research Funds for the Central Universities(grant no.63223056)the Frontiers Science Center for New Organic Matter at Nankai University(grant no.63181206).
文摘Van der Waals(vdW)contact,dominated by weak but ubiquitous vdW interactions,plays a significant role in diverse fields such as supramolecular chemistry,nanotechnology,and surface science.Accurate characterization of vdW contact at the single-molecule level remains challenging.Herein,we combine the scanning tunneling microscope break junction technique with first-principles calculations to study the mechanical and electrical characteristics of the alkane/Au vdW contact in an in-situ solution environment.The step-like conductance plateaus indicate a gradual desorption of alkyl chains in units of two methylene groups under force stretching.Two distinct charge transport channels,through the shortest C–H/Au pathway and the entire adsorbed alkyl chain,are identified.Furthermore,we discover that a higher electric field leads to increased conductance and stronger bonding of the alkane/Au vdW contact.These results unveil the intrinsic properties of vdW contact at the molecular and even atomic levels,which are crucial for exploring noncovalent interactions and advancing molecular sciences.
