Investigating the self-assembly of pH-sensitive switchable diamine surfactant using sum frequency generation spectroscopy and molecular dynamics simulations.

The responses of the N-alkyl diamine groups to variations in pH affect their conformations and surface activities, making them relevant to applications relying on interfacial interactions, such as controlled emulsification and mineral flotation. An in-depth understanding of interfacial self-assembly is crucial. Herein, a molecular-level study was performed to investigate the adsorption and self-assembly of N-dodecylpropane-1,3-diamine (DPDA) at the air-water (A/W) interface using sum frequency generation (SFG) spectroscopy and molecular dynamics (MD) simulations.

Using the pH sensitivity of switchable surfactants to understand the role of the alkyl tail conformation and hydrogen bonding at a molecular level in elucidating emulsion stability.

Hypothesis: The monoalkyl diamine surfactant, N-dodecylpropane-1,3-diamine (DPDA), is expected to exhibit a pH-dependent charge switchability. In response to pH changes, the interfacial self-assembly of DPDA becomes an intermediary constituent that can potentially modify the interfacial interactions and structural assembly of both the oil and water phases. Hence, we hypothesize that as we change the pH, DPDA will respond to it by changing its charge and alkyl tail conformation as well as the conformation of adjacent phases at the molecular level, consequently affecting emulsion formation and stability.

Visible Light-Assisted Coordination of a Rh(III)-BODIPY Complex to Guanine.

Most photodynamic therapeutics (PDTs) used in cancer treatment require oxygen to work efficiently to terminate cancer cells. These PDTs do not efficiently treat tumors in hypoxic conditions. Rh(III) polypyridyl complexes have been reported to have a photodynamic therapeutic effect in hypoxic conditions when exposed to UV light.

Standard-Free Absolute Quantitation of Antibody Deamidation Degradation and Host Cell Proteins by Coulometric Mass Spectrometry.

Proteomic absolute quantitation strategies mainly rely on the use of synthetic stable isotope-labeled peptides or proteins as internal standards, which are highly costly and time-consuming to synthesize. To circumvent this limitation, we recently developed a coulometric mass spectrometry (CMS) approach for absolute quantitation of proteins without the use of standards, based on the electrochemical oxidation of oxidizable surrogate peptides, followed by mass spectrometry measurement of the peptide oxidation yield. Previously, CMS was only applied for single-protein quantitation.