Modern Spectroscopy

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Modern Spectroscopy

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The C(1)-C(α) torsional potential function of 2-fluorostyrene from S1-S0 fluorescence in a supersonic jet

Single vibronic level fluorescence spectra of tram-2-fluorostyrene have been observed in a supersonic jet. Levels of the C(1)-C(a)torsional vibration up to u=8 are fitted to a potential function which shows that the molecule is quasi-planar with a barrier of I5+4 cm-’

The à 1B2u-X̃1Ag electronic absorption spectrum of 1,2,4,5-tetrafluorobenzene: rotational band contour and vibrational analysis relating to non-planarity in the à state

The vapour phase electronic absorption spectrum of 1,2,4,5-tetrafluorobenzene, in the region of the S1-S0 band system, has been photographed under conditions of high resolution. Computer simulation of the observed rotational contours has shown that all the most intense bands are type A and, therefore, that the electronic assignment is A ‘B2uX1Ag. The rotational constants in the A state are consistent with an out-of-plane angle of the C-F bonds of 11+4”. This is consistent with the result obtained by Okuyama et al., from the supersonic jet spectrum, that the fluorine atoms are out-of-plane in a “butterfly” configuration. Obser- vation of hot bands of the butterfly vibration, which are frozen out in the jet spectrum, provides strong support for the W-shaped potential function proposed by Okuyama et al. for this vibration in the A state

The 291-nm band system of 3-fluorostyrene: ground state vibrational assignments for the cis and trans rotamers from their supersonic jet spectra

Single vibronic level fluorescence spectra, with excitation in the O& 4 1;42& 42& and 29h bands of cis 3-fluorostyrene and in the 08 band of trans 3-fluorostyrene, have been obtained in a super-sonic jet. Assignments of these spectra show that some vibrational fundamentals, particularly those involving the part of the molecule in the region of the vinyl group, are appreciably different in the two rotamers. In the So electronic state the cis rotamer is 220 cm-’ lower in energy than the tram and this difference is increased to 495 cm-’ in S, . The cis-trans barrier is increased from 1150 cm-’ in S, to about 2500 cm-’ in S, but a strong Duschinsky effect, affecting the C(1)-C(cx) torsional vibration, makes the barrier in s, very uncertain

The C(1)-C(α) torsional potential function of cis- and trans-3-fluorostyrene by supersonic jet spectroscopy

Single vibronic level fluorescence spectra of cis- and trans-3-fluorostyrene in a supersonic jet has resulted in the determination of several C(1)-C(a) torsional vibrational levels of both rotamers. Fitting these to a torsional potential function shows that the cis rotamer is the more stable by 220cm-1

Spin Labeling of Surface Cysteines Using a Bromoacrylaldehyde Spin Label

UNLABELLED: Structural investigations of proteins and their biological complexes are now frequently complemented by distance constraints between spin labeled cysteines generated using double electron-electron resonance (DEER) spectroscopy, via site directed spin labeling (SDSL). Methanethiosulfonate spin label (MTSSL), has become ubiquitous in the SDSL of proteins, however, has limitations owing to its high number of rotamers, and reducibility. In this article we introduce the use of bromoacrylaldehyde spin label (BASL) as a cysteine spin label, demonstrating an advantage over MTSSL due to its increased selectivity for surface cysteines, eliminating the need to 'knock out' superfluous cysteine residues. Applied to the multidomain protein, His domain protein tyrosine phosphatase (HD-PTP), we show that BASL can be easily added in excess with selective labeling, whereas MTSSL causes protein precipitation. Furthermore, using DEER, we were able to measure a single cysteine pair distance in a three cysteine domain within HD-PTP. The label has a further advantage of comprising a sulfide in a three-bond tether, making it a candidate for protein binding and in-cell studies.SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00723-021-01350-1.</p

Divergent Antibody Repertoires Found for Omicron versus Wuhan SARS-CoV‑2 Strains Using Ig-MS

SARS-CoV-2 Omicron (B.1.1.529) and its subvariants are currently the most common variants of concern worldwide, featuring numerous mutations in the spike protein and elsewhere that collectively make Omicron variants more transmissible and more resistant to antibody-mediated neutralization provided by vaccination, previous infections, and monoclonal antibody therapies than their predecessors. We recently reported the creation and characterization of Ig-MS, a new mass spectrometry-based serology platform that can define the repertoire of antibodies against an antigen of interest at single proteoform resolution. Here, we applied Ig-MS to investigate the evolution of plasma antibody repertoires against the receptor-binding domain (RBD) of SARS-CoV-2 in response to the booster shot and natural viral infection. We also assessed the capacity for antibody repertoires generated in response to vaccination and/or infection with the Omicron variant to bind to both Wuhan- and Omicron-RBDs. Our results show that (1) the booster increases antibody titers against both Wuhan- and Omicron- RBDs and elicits an Omicron-specific response and (2) vaccination and infection act synergistically in generating anti-RBD antibody repertoires able to bind both Wuhan- and Omicron-RBDs with variant-specific antibodies