der Ludwig-Maximilians-Universität München Structural Characterization of Chaperone Assisted Folding and Assembly of RuBisCO

for giving me the opportunity to do my PhD research in this laboratory and for their supervision, advice, and guidance throughout the entire period of my study. I wish to express my warm and sincere thanks to Prof. Dr. Konstanze Winklhofer for correcting my dissertation and being the co-referee of my thesis committee. I would like to thank Dr. Andreas Bracher for all the crystallization help, Oana, Günter and Dr. Beate Rockel for all the help during the electron microscopy sessions. I would like to thank Prof. Dr. Jürgen Soll for providing us Arabidopsis cDNA. I wish to extend my warmest thanks to Andrea, Silke, Elisabeth, Grampp, Emmanuel and Nadine for assisting me in many ways. I would like to thank Sandra, Kausik and all my colleagues who have helped me with my work in the Department. I am also greatly indebted to my teachers in the past, Dr. K. M. Divakar and Late Dr. M. D. Kulashekaran for their constant support and motivation. I am immensely grateful for my husband, who is also my colleague, Karnam Vasudeva Rao who has been like a pillar of support to me. Without his love, encouragement, understanding and constant guidance, it would have been impossible fo

Attempts to Delineate the Relative Contributions of Changes in Hydrophobicity and Packing to Changes in Stability of Ribonuclease S Mutants

While the hydrophobic driving force is thought to be a majorcontributor to protein stability, it is difficult to experimentallydissect out its contribution to the overall free energy of folding. Wehave made large to small substitutions of buried hydrophobic residuesat positions 8 and 13 in the peptide/protein complex, RNase-S, and havecharacterized the structures by X-ray crystallography. Thethermodynamics of association of these mutant S peptides with S proteinwas measured in the presence of different concentrations of methanoland ethanol. The reduction in the strength of the hydrophobic drivingforce in the presence of these organic solvents was estimated fromsurface-tension data as well as from the dependence of the $\Delta C_p$ ofprotein/peptide binding on the alcohol concentration. The dataindicated a decrease in the strength of the hydrophobic driving forceof about 30-40% over a 0-30% range of the alcohol concentration. Weobserve that large to small substitutions destabilize the protein.However, the amount of destabilization, relative to the wild type, isindependent of the alcohol concentration over the range of alcoholconcentrations studied. The data clearly indicate that decreasedstability of the mutants is primarily due to the loss of packinginteractions rather than a reduced hydrophobic driving force andsuggest a value of the hydrophobic driving force of less than 18 cal mol^-^1 Å2