Design of a molecular memory element with an alternating circular array of dipolar rotors and rotation suppressors.
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ABSTRACT:
SUBMITTER: Miyazaki T
PROVIDER: S-EPMC8163413 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:We report the synthesis of five dicarboxylic acid-substituted dipolar molecular rotors for the use as linker molecules in metal-organic frameworks (MOFs). The rotor molecules exhibit very low rotational barriers and decent to very high permanent, charge free dipole moments, as shown by density functional theory calculations on the isolated molecules. Four rotors are fluorescent in the visible region. The linker designs are based on push-pull-substituted phenylene cores with ethynyl spacers as rotational axes, functionalized with carboxylic acid groups for implementation in MOFs. The substituents at the phenylene core are chosen to be small to leave rotational freedom in solids with confined free volumes. The dipole moments are generated by electron-donating substituents (benzo-1,3-dioxole, benzo-1,4-dioxane, or benzo-2,1,3-thiadiazole annelation) and withdrawing substituents (difluoro, or dicyano substitution) at the opposite positions of the central phenylene core. A combination of 1,4-dioxane annelation and dicyano substitution generates a theoretically predicted, very high dipole moment of 10.1 Debye. Moreover, the molecules are sufficiently small to fit into cavities of 10 Å3. Hence, the dipolar rotors should be ideally suited as linkers in MOFs with potential applications as ferroelectric materials and for optical signal processing.
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Project description:Many genome-processing reactions, including transcription, replication and repair, generate DNA rotation. Methods that directly measure DNA rotation, such as rotor bead tracking1-3, angular optical trapping4 and magnetic tweezers5, have helped to unravel the action mechanisms of a range of genome-processing enzymes that includes RNA polymerase (RNAP)6, gyrase2, a viral DNA packaging motor7 and DNA recombination enzymes8. Despite the potential of rotation measurements to transform our understanding of genome-processing reactions, measuring DNA rotation remains a difficult task. The time resolution of existing methods is insufficient for tracking the rotation induced by many enzymes under physiological conditions, and the measurement throughput is typically low. Here we introduce origami-rotor-based imaging and tracking (ORBIT), a method that uses fluorescently labelled DNA origami rotors to track DNA rotation at the single-molecule level with a time resolution of milliseconds. We used ORBIT to track the DNA rotations that result from unwinding by the RecBCD complex, a helicase that is involved in DNA repair9, as well as from transcription by RNAP. We characterized a series of events that occur during RecBCD-induced DNA unwinding-including initiation, processive translocation, pausing and backtracking-and revealed an initiation mechanism that involves reversible ATP-independent DNA unwinding and engagement of the RecB motor. During transcription by RNAP, we directly observed rotational steps that correspond to the unwinding of single base pairs. We envisage that ORBIT will enable studies of a wide range of interactions between proteins and DNA.
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Project description:Fluorescent molecular rotor dyes, including Cy3, Cy5, and Alexa Fluor 555, dissolved in micron-sized aqueous droplets (microdroplets) in oil were excited, and the fluorescence intensity was recorded as function of time. We observed lengthening of the fluorescence lifetime of these dyes at the water-oil periphery, which extended several microns inward. This behavior shows that intramolecular rotation is restricted at and near the microdroplet interface. Lengthened lifetimes were observed in water microdroplets but not in microdroplets composed of organic solvents. This lifetime change was relatively insensitive to added glycerol up to 60%, suggesting that solution viscosity is not the dominant mechanism. These restricted intramolecular rotations at and near the microdroplet periphery are consistent with the reduced entropy observed in chemical reactions in microdroplets compared to the same reaction conditions in bulk solution and helps us further understand why microdroplet chemistry differs so markedly from bulk-phase chemistry.
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Project description:Molecular dynamics simulations of the response to oscillating electric field elicited from an altitudinal dipolar molecular rotor mounted on the Au(111) surface and previously studied experimentally in static fields show unidirectional rotation in one of the three pairs of conformational enantiomers. The simulations are based on the universal force field and take into account electronic friction in the metal through its effect on the image charges. The rotor consists of two cobalt sandwich posts whose upper decks carry a biphenyl-like rotator with a dipole moment perpendicular to the rotation axle, mounted parallel to the surface. A phase diagram of rotor performance at 10 K as a function of field frequency and amplitude contains five unidirectional rotation regions: synchronous, half-synchronous (every other cycle skipped), quarter-synchronous (only indistinctly), asynchronous, and essentially no response. The nature of the subharmonic "single-molecule parametric oscillator" behavior is understood in mechanistic detail. Simulations at higher temperatures distinguish the thermal ("Brownian") and driven regimes of rotation, elucidated in terms of time-dependent potential energy surfaces for the rotation.
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Project description:BackgroundEntrants into UK surgical specialty training undertake a 2-year programme of core surgical training, rotating through specialties for varying lengths of time, at different hospitals, to gain breadth of experience. This study aimed to assess whether these variables influenced core surgical trainee (CST) work productivity.MethodsIntercollegiate Surgical Curriculum Programme portfolios of consecutive CSTs between 2016 and 2019 were examined. Primary outcome measures were workplace-based assessment (WBA) completion, operative experience and academic outputs (presentations to learned societies, publications and audits).ResultsA total of 344 rotations by 111 CSTs were included. Incremental increases in attainment were observed related to the duration of core surgical training rotation. The median number of consultant-validated WBAs completed during core surgical training were 48 (range 0-189), 54 (10-120) and 75 (6-94) during rotations consisting of 4-, 6- and 12-month posts respectively (P < 0·001). Corresponding median operative caseloads (as primary surgeon) were 84 (range 3-357), 110 (44-394) and 134 (56-366) (P < 0·001) and presentations to learned societies 0 (0-12), 0 (0-14) and 1 (0-5) (P = 0·012) respectively. Hospital type and specialty training theme were unrelated to workplace productivity. Multivariable analysis identified length of hospital rotation as the only factor independently associated with total WBA count (P = 0·001), completion of audit (P = 0·015) and delivery of presentation (P = 0·001) targets.ConclusionLonger rotations with a single educational supervisor, in one training centre, are associated with better workplace productivity. Consideration should be given to this when reconfiguring training programmes within the arena of workforce planning.
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