Lab 03 Part I Spring 2012 revised

Lab 03 Part I Spring 2012 revised - BSCI330 Laboratory...

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BSCI330 Laboratory Manual Spring 2012 1 | P a g e LAB EXERCISE 3 – Part I Physical Properties of Proteins and Methods of Isolation Figure 1. Basic structure of proteins From: Molecular Biology of the Cell (© Garland Science 2008) I. Introduction From their initial discovery and basic characterization in the 1830s, proteins have been long regarded as essential components of all living systems. As you’ll recall from previous biology courses, proteins are polymers consisting of strings of amino acid monomers covalently linked together via peptide bonds (Figure 1). The primary structure of a protein is determined by the linear order of its amino acids. There are 20 naturally occurring amino acids used to build proteins, each composed of a similar backbone structure with a unique chemical group called a side chain or R group. As R groups differ in their chemical structures and thus chemical properties, each type of amino acid differs in its chemical nature 1 . Thus, given that proteins are, at their core, strings of amino acid subunits, the overall chemical property of any given protein is dependent upon its amino acid composition. Of course, proteins in cellular environments do not remain unstructured strings of monomers, but rather achieve complex, two dimensional and three dimensional shapes (Figure 1), determined by internal interactions among amino acid backbone functional groups (amino groups, carboxyl groups) and among chemically complementary R groups, as well as by external interactions with surrounding (polar) water molecules. Next week, you will have a chance to investigate the three dimensional architecture of proteins; however, the goal of this week’s lab is, in part, to appreciate how chemical properties of proteins determine their interactions with water, and how this can be exploited to selectively isolate proteins from tissues and cells. 1 For more information on amino acid structure, see panel 3-1 in your textbook.
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BSCI330 Laboratory Manual Spring 2012 2 | P a g e Functionally, proteins are the workhorses of the cell, responsible for carrying out virtually all of a given cell’s tasks, from the transport of molecules into and out of the cell, to the catalysis of metabolic reactions; from the regulation of gene expression, to the duplication and division of the genome. In fact, to truly begin to understand a given cellular process is to have an appreciation for at least a few of the proteins involved and the interactions they undergo. It is no surprise that, given all of this, proteins are by far the most variable of all biological macromolecules in terms of structure, size, and function. It is also no surprise that the biochemical isolation and analysis of proteins from cells continues to be an integral component of experimental cell biology. Tissue Fractionation
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This note was uploaded on 02/27/2012 for the course BSCI 330 taught by Professor Payne during the Spring '08 term at Maryland.

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Lab 03 Part I Spring 2012 revised - BSCI330 Laboratory...

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