N‐Methyl‐trimethylacetamide in Thin Films Displays Infrared Spectra of π‐Helices, with Visible Static and Dynamic Growth Phases, and then a β‐Sheet

Abstract

The simplest (minimal) peptide model is HCONHCH3. An increase in the π-helix content with increased substitution in the acyl portion suggested the examination of N-methyl-trimethylacetamide) (NMT). NMT displays spectra, in which there is evolution of a set of helices defined by their amide I maxima near 1686 (3(10)), 1655 (first π), and, most importantly, at 1637 cm(-1) (π). Expanded thin-film infrared spectroscopy (XTFIS) shows pauses or slow stages, which are identified as static phases followed by dynamic phases with the incremental gain or loss of a helix turn. In addition, absorbance at 1637 cm(-1) suddenly increases at 82.1 s (30% over 0.3 s), indicating a phase change and crystallization of the π-helix, along with a coincidental decrease in the absorbance for the first π-helix. A sharp peak occurs at the maximum of the phase change at 82.5 s, representing a pure NMT π-helix. The spectra then undergo a decreasing general absorption loss over 150 s, with the π-helix evolving further to an antiparallel β-sheet fragment. The spectral quality arises from the immobilization of polar molecules on polar surfaces. The crystal structure is that of an antiparallel β-sheet.

Low polarity water, a novel transition species at the polyethylene–water interface

“…Spectra (usually 100 in a run) were acquired using a Bruker Vertex 70 using mostly low signal strength (Sg, 100) and short scan times (0.1 s) as explained in our previous papers, 10,11,15,16 using a Bruker Equinox 55/S. The polyethylene cells were made from LDPE film purchased from a supermarket.…”

N‐Alkylacylamides in Thin Films Display Infrared Spectra of 310‐, α‐, and π‐Helices with Visible Static and Dynamic Growth Phases

“…The behavior of another N-methylacylamide, N-methyl-trimethylacetamide (NMT) is described in a related article. [12] Quasiplanar forms are conformational isomers of the helices, in which much of the vibrational coupling that enhances helix absorption is lost; this is the first time that such a change has been explicitly recognized.…”

Heterogenization of complexes with redox active ligands for hydrogen evolution reaction.

“…One way to combine the benefits of homogeneous and heterogeneous catalysts is through the immobilization of known catalysts onto solid surfaces for letting them work in heterogeneous conditions. [82][83][84][85][86] Abhishek Although the relatively large overpotential for these modified electrodes limits the further application, however, the ligand centered HER mechanism opens the door to an alternative pathway and strategies for HER catalysts that does not involved metal hydride.…”