Koshland, Daniel

This concerted model assumes furthermore that the symmetry of the molecule is conserved so that the activity of all its subunits is either equally low or equally high, that is, all structural changes are concerted. Subsequently Daniel Koshland, University of California, Berkeley, postulated a sequential model in which each subunit is allowed independently to change its tertiary structure on substrate binding. In this model tertiary structural changes in the subunit with bound ligand alter the interactions of this... 

Such beliefs are drawing respectability from the tendency to reduce human behavior to evolutionary explanations. Neo-Darwinist theories seem to explain why some people thrive in the competitive world of the 1990s and others do not. Promoting these theories, some scientists argue that genetics is important in selecting people with superior skills. Says, Daniel Koshland, molecular biologist and former editor of Science - As society... 

Other characteristics of life have been formulated by Daniel E. Koshland Jr. (University of California at Berkeley) as the Seven Pillars of Life . They are as follows ... 

In the second model, the sequential model (Fig. 5-15b), proposed in 1966 by Daniel Koshland and colleagues, ligand binding can induce a change of conformation in an individual subunit. A conformational change in one subunit makes a similar change in an... 

This is referred to as induced fit, a mechanism postulated by Daniel Koshland in 1958. Induced fit serves to bring specific functional groups on the enzyme into the proper position to catalyze the reaction. The conformational change also permits formation of additional weak bonding interactions in the transition state. In either case, the new enzyme conformation has enhanced catalytic properties. As we have seen, induced fit is a common feature of the reversible binding of ligands to proteins (Chapter 5). Induced fit is also important in the interaction of almost every enzyme with its substrate. 

There are essentially two types of control mechanisms for biochemical switching allosteric cooperative transition and reversible chemical modification. Allosteric cooperativity, which was discussed in Chapter 4, was discovered in 1965 by Jacques Monod, Jefferies Wyman, and Jean-Picrrc Changeux [143], and independently by Daniel Koshland, George Nemethy and David Filmer [116]. The molecular basis of this phenomenon, which is well understood in terms of three-dimensional protein crystal structures and protein-ligand interaction, is covered in every biochemistry textbook [147] as well as special treatises [215],... 

An attempt was made recently to find out how sensitively the regulatory system that controls the cell cycle and cell proliferation responds to signal input. Ferrell et found that, in intact oocytes, the response is ultrasensitive , a kinetic characterization introduced by Daniel E. Koshland Jr.26 (Ultrasensitivity has been defined as the response of an enzyme that is more sensitive to changes in the concentration of the substrate than an enzyme with a normal hyperbolic response, according to the Michaelis-Menten equation. One can also use the Hill coefficient (wh) to indicate hyperbolic (Michaelis-Menten) sensitivity ( h = 1-0), ultrasensitivity ( h > l)j and subsensitivity ( h <... 

Figure 34.28. Bacterial Flagella. Electron micrograph of S. typhimurium shoves flagella in a bundle. [Courtesy of Dr. Daniel Koshland, Jr.]...

In a similar vein, Daniel E. Koshland Jr., the editor of the premier American scientific journal Science, a man with extensive career experience in the chemistry and pharmacology of opiate drugs, commented in an editorial entitled "The War Program Experiment on Drugs" (Koshland 1989) ... 

Podolsky, M.L. 1997. Cures Out of Chaos How Unexpected Discoveries Led to Breakthroughs in Medicine and Health, with a foreword by Daniel E. Koshland, Jr. Amsterdam Harwood Academic Publishers. 

Today we know that proteins are flexible molecules. This led Daniel E. Koshland, Jr., to propose a more sophisticated model of the way enzymes and substrates interact. This model, proposed in 1958, is called the induced fit model (Figure 20.3b). In this model the active site of the enzyme is not a rigid pocket into which the substrate fits precisely rather, it is a flexible pocket that approximates the shape of the substrate. When the substrate enters the pocket, the active site "molds" itself around the substrate. This produces the perfect enzyme-substrate "fit."... 

The induced-fit theory first described by Daniel E. Koshland. Jr., in 1958 is one of the most fundamental discoveries of our age and is a development of Emil Fischer s well-known lock and key theory,it should be noted that an important characteristic of the key-lock theory is that the enzyme accommodates the substrate without having to change the shape of the active site however, in the induced-fit model, the enzyme changes shape when it reacts, like a glove into which a hand is thrust. To visualize the concepts of induced fit and keylock, two binding models are illustrated in Fig. 1. 

D. E. Koshland, Jr. 1, 10, 18 John S. Kovach 5 Gisela Kramer 20 Edwin G. Krebs 5, 16, 18 H. A. Krebs 1, 18 Nurith Kurn 9 D. A. Kyriakidis 15 M. R. Lakshmanan 18 M. Daniel Lane 8, 18 Henry A. Lardy 18 Joseph Lamer 3 Michel Lazdunski 6 P. J. Lea 20 Robert J. Lefkowitz 17 Albert L. Lehninger 18 Luis F. Leloir 18 James F. Lenney 17 Alexander Levitzki 10 Heng-Chun Li 21 Anthony W. Linnane 2 Fritz Lipmann 18 John M. Lowenstein 18 W. C. Lucchesi 15 Ronald W. McCune 15... 

Using lanthanum fluoride as a carrier, Seaborg isolated a weighable sample of plutonium in August 1942. At the same time, Isadore Perlman and William J. Knox explored the peroxide method of separation John E. Willard studied various materials to determine which best adsorbed plutonium Theodore T. Magel and Daniel K. Koshland, Jr., researched solvent-extraction processes and Harrison S. Brown and Orville F. Hill performed experiments into volatility reactions. 

---