Equilibrium versus Nonequilibrium Peptide Dynamics: Insights into Transient 2D IR Spectroscopy.

Over the past two decades, two-dimensional infrared (2D IR) spectroscopy has evolved from the theoretical underpinnings of nonlinear spectroscopy as a means of investigating detailed molecular structure on an ultrafast time scale. The combined time and spectral resolution over which spectra can be collected on complex molecular systems has led to the precise structural resolution of dynamic species that have previously been impossible to directly observe through traditional methods. The adoption of 2D IR spectroscopy for the study of protein folding and peptide interactions has provided key details of how small changes in conformations can exert major influences on the activities of these complex molecular systems.

Tyrosine as a Non-perturbing Site-Specific Vibrational Reporter for Protein Dynamics.

The ability to detect changes in the local environment of proteins is pivotal to determining their dynamic nature during many biological processes. For this purpose, the utility of the tyrosine ring breathing vibration as a sensitive infrared reporter for measuring the local electric field in protein is investigated. Variations in the bandwidth of this vibrational transition in a variety of solvents indicate differences in microenvironment affect the inhomogeneous broadening and thus the frequency distribution.

Two-Dimensional Infrared Study of Vibrational Coupling between Azide and Nitrile Reporters in a RNA Nucleoside.

The vibrations in the azide, N3, asymmetric stretching region and nitrile, CN, symmetric stretching region of 2'-azido-5-cyano-2'-deoxyuridine (N3CNdU) are examined by two-dimensional infrared (2D IR) spectroscopy. At earlier waiting times, the 2D IR spectrum shows the presence of both vibrational transitions along the diagonal and off-diagonal cross peaks indicating vibrational coupling. The coupling strength is determined from the off-diagonal anharmonicity to be 66 cm(-1) for the intramolecular distance of ∼7.

Quantitation of plasma apolipoprotein A-I using two monoclonal antibodies in an enzyme-linked immunosorbent assay.

A rapid sandwich enzyme-linked immunosorbent assay (ELISA) for the quantitation of human apolipoprotein (apo) A-I was developed. The assay uses a pair of noncompeting purified monoclonal antibodies to detect apoA-I in plasma. The antibodies used in this assay were selected because they bind greater than 90% of radioiodinated high density lipoprotein (HDL), they identify "fresh" nondeamidated epitopes on apoA-I, and they have comparable binding affinities for isolated HDL and HDL in plasma.

Two new monoclonal antibody-based enzyme-linked assays of apolipoprotein B.

We describe two new monoclonal antibody-based, solid-phase immunoenzymometric assays for the quantification of apolipoprotein (apo) B in plasma: a competitive assay and a direct assay. For both, we utilize 96-well microtiter plates and native low-density lipoprotein (LDL) for preparing the standard curve. A single monoclonal antibody, MB24, is used in the competitive assay.