Spotlights pubs.acs.org/JPCL
Spotlights: Volume 8, Issue 12
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BLUE-SHIFTED GREEN FLUORESCENT PROTEIN HOMOLOGUES ARE BRIGHTER THAN ENHANCED GREEN FLUORESCENT PROTEIN UNDER TWO-PHOTON EXCITATION Genetically encoded fluorescent protein probes with enhanced two-photon brightness are in great demand in biomedical research, e.g., in the area of live brain imaging. Physiologically relevant data collection is limited because the high intensities of the excitation laser lead to heat-induced damage of the tissue. By improving the two-photon brightness of a fluorescent protein, an equivalent fluorescence signal can be acquired with a lower laser power and thus less heating, thereby increasing the time available for imaging before damaging brain tissue. Molina et al. (10.1021/acs.jpclett.7b00960) developed a physical model that describes the effect of protein electrostatics on the strength of two-photon absorption in a series of green fluorescent protein (GFP) homologues. Using this model, they found several GFP-type proteins with considerably enhanced twophoton brightness (up to 2.5 times compared to commonly used EGFP) that would enable more efficient two-photon imaging in neuroscience, including brain imaging.
interactions, dipole moments, and polarizabilities are represented as well as on how the molecular motion is described. These challenges have hindered the development of a unified interpretation of the vibrational spectrum of ice in terms of the corresponding MD. Moberg et al. (10.1021/acs.jpclett.7b01106) demonstrate that quantum many-body MD (MB-MD) simulations lead to a unified interpretation of the vibrational spectra of ice Ih in terms of the structure and dynamics of the underlying hydrogen-bond network. The authors assign all features of the IR and Raman spectra in the OH stretching region by taking into account both the symmetry and the delocalized nature of the lattice vibrations as well as the local electrostatic environment experienced by each water molecule within the crystal.
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NOVEL LIPOSOME-BASED SURFACE-ENHANCED RAMAN SPECTROSCOPY (SERS) SUBSTRATE Surface-enhanced Raman spectroscopy (SERS) offers researchers the ability to probe the vibrational spectrum of single molecules. SERS has enormous potential for biophysical studies, in particular, because of its sensitivity, molecular specificity, and narrow peak bandwidth, but biological compatibility remains a challenge. The ideal SERS substrates would possess high enhancement and improved reproducibility while allowing for the measurement of biological species in a cell-like environment. Lum et al. (10.1021/acs.jpclett.7b00694) constructed liposome-based SERS substrates in which the biological probe molecule is encapsulated inside the aqueous liposome compartment and metallic elements are assembled using the liposome as a scaffold. The probe molecule is not in contact with the metallic surfaces. The authors used finitedifference time-domain calculations to predict SERS enhancements for the nanoparticle-on-mirror substrates that they studied experimentally. They found that the substrate exhibits high SERS enhancement of 8 × 106, improved reproducibility over typical SERS substrates, and the potential to exhibit greatly improved biocompatibility.
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MOLECULAR ORIGIN OF THE VIBRATIONAL STRUCTURE OF ICE Ih Despite the fact that more than 50 years have passed since the first measurements of the vibrational spectra of ice Ih, the assignment of the different features of the infrared (IR) and Raman spectra is still controversial. In principle, molecular dynamics (MD) simulations should provide direct insights into the origin of all different spectroscopic features; however, the accuracy of IR and Raman spectra calculated from an MD simulation depends on the accuracy with which the molecular © 2017 American Chemical Society
Published: June 15, 2017 2757
DOI: 10.1021/acs.jpclett.7b01433 J. Phys. Chem. Lett. 2017, 8, 2757−2757
