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Proton transfer remains one of the most fundamental processes in chemistry and biology. Superphotoacids provide an excellent platform to delineate the excited-state proton transfer (ESPT) mechanism on ultrafast timescales and enable one to precisely control photoacidity and other pertinent functionalities such as fluorescence. We modified the GFP core ( p-HBDI chromophore) into two series of highly fluorescent photoacids by fluorinating the phenolic ring and conformationally locking the backbone (i.e., biomimetics). The trifluorinated derivatives, M3F and P3F, represent two strongest superphotoacids with p K* of ‒5.0 and ‒5.5, respectively, and they can efficiently transfer a proton to organic solvents like methanol. Tunable femtosecond stimulated Raman spectroscopy (FSRS) and femtosecond transient absorption (fs-TA) were employed to dissect the ESPT of M3F and P3F in methanol, particularly with structural dynamics information. By virtue of resonantly enhanced FSRS signal and global analysis of fs-TA spectra, we revealed an inhomogeneous ESPT mechanism consisting of three parallel routes following the initial small-scale proton motion and contact ion-pair formation within ~300 fs. The first route consists of ultrafast protolytic dissociation facilitated by the pre-existing, largely optimized H-bonding chain; the second route is limited by solvent reorientation that establishes a suitable H-bonding wire for proton separation; the third route is controlled by rotational diffusion that requires rotation of the anisotropically reactive photoacid in a bulky solvent with a complex H-bonding structure over larger distances. Furthermore, we provided new design principles of enhancing photoacidity in a synergistic manner: incorporating electron-withdrawing groups into proximal (often as "donor") and distal (often as "acceptor") ring moieties of the dissociative hydroxyl group to lower the ground-state p K and increase the Δp K, respectively.
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Name: The journal of physical chemistry. B
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Application of principles and practices of engineering science to the transformation, design, and manufacture of substances on an industrial scale.
Energy that is generated by the transfer of protons or electrons across an energy-transducing membrane and that can be used for chemical, osmotic, or mechanical work. Proton-motive force can be generated by a variety of phenomena including the operation of an electron transport chain, illumination of a PURPLE MEMBRANE, and the hydrolysis of ATP by a proton ATPase. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed, p171)
An approach, process, or methodology which emphasizes credible evidence and the best available scientific knowledge, judiciously integrated to achieve the best possible outcomes in structural design. For example, the design of a new OUTPATIENT CLINIC might incorporate a review of published research on outpatient clinic design, decisions on similar past projects, along with interviews with staff and consumers.
Microscopy of specimens stained with fluorescent dye (usually fluorescein isothiocyanate) or of naturally fluorescent materials, which emit light when exposed to ultraviolet or blue light. Immunofluorescence microscopy utilizes antibodies that are labeled with fluorescent dye.
A complex of enzymes and PROTON PUMPS located on the inner membrane of the MITOCHONDRIA and in bacterial membranes. The protein complex provides energy in the form of an electrochemical gradient, which may be used by either MITOCHONDRIAL PROTON-TRANSLOCATING ATPASES or BACTERIAL PROTON-TRANSLOCATING ATPASES.