Effects of Methyl Side Chains on the Microsolvation Structure of Protonated Tripeptides.

The infrared predissociation spectra of the GlyH(HO) and AlaH(HO) clusters are presented and analyzed with the goal of revealing the influence of methyl side chains on the microsolvated structures of these flexible tripeptides. We have shown previously that the presence of methyl side chains can modulate the strengths of the intramolecular hydrogen bonds, thereby influencing the structures adopted by the bare tripeptides composed of glycine and alanine residues. This effect was attributed to the electron-donating nature of the methyl group, whose presence alters the proton affinities of the functional groups that are involved in hydrogen bonding.

Conformational Changes Induced by Methyl Side-Chains in Protonated Tripeptides Containing Glycine and Alanine Residues.

We present a systematic study of the conformational and isomeric populations in gas-phase protonated tripeptides containing glycine and alanine residues using infrared predissociation spectroscopy of cryogenically cooled ions. Specifically, the protonated forms of Gly-Gly-Gly, Ala-Gly-Gly, Gly-Ala-Gly, Gly-Gly-Ala, Ala-Ala-Gly, Ala-Gly-Ala, Gly-Ala-Ala, and Ala-Ala-Ala allow us to sample all permutations of the methyl side-chain position, providing a comprehensive view of the effects of this simple side-chain on the 3-D structure of the peptide. The individual structural populations for all but one of these peptide species are determined via conformer-specific IR-IR double-resonance spectroscopy and comparison with electronic structure predictions.

Comment on "Microhydration of Biomolecules: Revealing the Native Structures by Cold Ion IR Spectroscopy".

This Viewpoint presents a re-examination of the conclusions of a study reported in (Saparbaev, . 2021, 12, 907) that compared the structure of microsolvated ions formed by electrospray ionization to those formed in the gas-phase a previously published cryogenic ion trap approach. We conducted additional experiments that clearly show that most of the observed differences in the IR spectra can be accounted for by considering the different spectroscopic action schemes used to obtain them.

Continuous measurements of volatile gases as detection of algae crop health.

Algae cultivation in open raceway ponds is considered the most economical method for photosynthetically producing biomass for biofuels, chemical feedstocks, and other high-value products. One of the primary challenges for open ponds is diminished biomass yields due to attack by grazers, competitors, and infectious organisms. Higher-frequency observations are needed for detection of grazer infections, which can rapidly reduce biomass levels.

Direct Measurement of the Visible to UV Photodissociation Processes for the PhotoCORM TryptoCORM.

PhotoCORMs are light-triggered compounds that release CO for medical applications. Here, we apply laser spectroscopy in the gas phase to TryptoCORM, a known photoCORM that has been shown to destroy Escherichia coli upon visible-light activation. Our experiments allow us to map TryptoCORM's photochemistry across a wide wavelength range by using novel laser-interfaced mass spectrometry (LIMS).

Competition between Solvation and Intramolecular Hydrogen-Bonding in Microsolvated Protonated Glycine and β-Alanine.

Infrared predissociation (IRPD) spectroscopy is used to reveal and compare the microsolvation motifs of GlyH(HO) and β-AlaH(HO). The chemical structure of these amino acids differ only in the length of the carbon chain connecting the amine and carboxyl terminals, which nonetheless leads to a significant difference in the strength of the intramolecular C═H-N hydrogen bond in the unsolvated ions. This difference makes them useful in our studies of the competition between solvation and internal hydrogen bonding interactions.

Microsolvation Structures of Protonated Glycine and l-Alanine.

The IR predissociation spectra of microsolvated glycine and l-alanine, GlyH(HO) and AlaH(HO) , n = 1-6, are presented. The assignments of the solvation structures are aided by HO/DO substitution, IR-IR double resonance spectroscopy, and computational efforts. The analysis reveals the water-amino acid as well as the water-water interactions, and the subtle effects of the methyl side chain in l-alanine on the solvation motif are also highlighted.