You Are Trying to Determine the Sequence of a Protein

question 85

Essay

You are trying to determine the sequence of a protein that you know is pure. Give the most likely explanation for each of the following experimental observations. You may use a simple diagram for your answer.
(a) The Sanger reagent (FDNB, fluorodinitrobenzene) identifies Ala and Leu as amino-terminal residues, in roughly equal amounts.
(b) Your protein has an apparent M_r of 80,000, as determined by SDS-polyacrylamide gel electrophoresis. After treatment of the protein with performic acid, the same technique reveals two proteins of M_r 35,000 and 45,000.
(c) Size-exclusion chromatography (gel filtration) experiments indicate the native protein has an apparent M_r of 160,000.

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Definitions:

Four-Firm Concentration Ratio

The four-firm concentration ratio is a measure of market concentration, calculated by the combined market share of the four largest firms within an industry, indicating the level of competition.

Herfindahl Index

A measure of market concentration used to evaluate the level of competition within an industry.

Market Shares

The portion of a market controlled by a particular company or product, often expressed as a percentage of total sales.

Herfindahl Index

A measure of the concentration and competitiveness of an industry, calculated by summing the squares of the market shares of each firm within the industry.