Molecular Differences of Coronavirus Variants
Prabin Baral

Abstract: Despite widespread availability of vaccines against SARS-CoV-2 infections, the virus continues to acquire new mutations. Highly transmissive Omicron and Delta variants surged after the waves of the Original, Alpha, and Beta variants. Although current vaccines offer protection against all known variants of concern, variants still can exhibit some ability to dodge the immune system. For example, in the case of the Delta variant it was found that neutralizing antibodies from prior infections or vaccines showed reduced molecular binding to the corona virus spike protein. I will discuss the molecular structural changes caused by the mutations in the receptor-binding part of the spike protein of some of these variants. I will discuss the resulting effects on the ability of a coronavirus to bind to a cell’s surface protein, as well as the effects on the binding of neutralizing antibodies to the coronavirus. We find that the slightly altered receptor-binding beta-loop-beta molecular motif in the spike protein of the Delta variant causes weaker binding to some antibody proteins that makes vaccines likely to be less effective compared to the Alpha and Beta variants. Tracking the structural changes of the virus spike protein receptor-binding domain due to various mutations will allow determination of antibody- and cellular protein binding interfaces that can explain on a molecular level the increased infectivity and increased immune evasion by different variants. This information can also be used to design more effective vaccines.

Many-Body Effects in Atomic Ensembles Probed by Optical 2D Coherent Spectroscopy Danfu Liang

Abstract: Neutral atoms can interact without a permanent dipole moment due to the transition-induced dipole moment. The interaction plays an essential role in many-body effects, such as energy shifts and changes in dephasing rates. In addition, its long-range nature has confirmed the necessity of including the interactions in the study of many-body systems. This talk focuses on interacting alkali-metal atomic ensembles to unveil the critical contributions of dipole-dipole interactions in many-body physics by using optical two-dimensional coherent spectroscopy (2DCS).