# P968: AFM force-distance, single molecule spectroscopy of titin: An undergraduate physical chemistry laboratory experiment

**Author**:

Zbigniew L. Gasyna, The University of Chicago, USA
**Co-Author**: Justin E. Jurelier and Norbert F. Scherer, University of Chicago, USA

**Date**: 8/7/14

**Time**: 10:15 AM – 10:35 AM

**Room**: MAN 123

**Related Symposium**: S56

A force-distance spectroscopy experiment using Atomic Force Microscopy (AFM) proposed for an undergraduate Physical Chemistry laboratory course is described. Force-distance spectroscopy is carried out in aqueous solution on a single molecule of I270 recombinant poly-protein that corresponds to the Ig 27 domain of human titin protein. Force-extension curves obtained by AFM measurements are analyzed to determine the persistence length, the contour length of the I270 protein domain, and contour length of the whole poly-protein molecule, i.e. the several I270 domains, by application of a worm-like-chain (WLC) model of biopolymer elasticity.

# P846: Application of programming in SCF calculations of the energy and vibrational properties of diatomic, two-electron molecules

**Author**:

Zbigniew L. Gasyna, The University of Chicago, USA
**Co-Author**:

**Date**: 8/6/14

**Time**: 3:05 PM – 3:25 PM

**Room**: LMH 176

**Related Symposium**: S55

Derivation of the Hartree-Fock Self-Consistent-Field (SCF) method is a standard topic in the upper level undergraduate quantum chemistry courses. Diatomic, two-electron molecules are simple enough to be amenable to application of programming languages at the undergraduate level for computation of the system energy and electronic properties. This paper will discuss RHF-SCF calculations employing minimal basis sets of Gaussian functions for diatomic, two-electron systems using several computational approaches. A design of undergraduate computational projects based on programming in C/C++ as well as in Matlab and Mathematica will be presented. SCF calculations on diatomic molecules in the Born-Oppenheimer approximation provide means for evaluation of interatomic potential and the dissociation energy. Based on the interatomic potential, the quantum states energies associated with the vibrational states of the diatomic molecule can be computed using the discrete value representation (DVR) of the Schrdinger equation for the vibrational motion. Subsequently, theoretical roto-vibrational transitions are computed from the quantum states energies. Quadratic fits to Fortrat diagrams are used to compute rotational constants of each vibrational level.