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Greetings. Welcome to this principles of biochemistry lecture series.
I am Jerry Feigenson.
I am a professor in the Department of
Molecular Biology and Genetics at Cornell University in the USA.
In the fifth lecture,
you saw that multiple folds can occur in a single polypeptide chain
and that more than one chain can associate in what is called quaternary structure.
That quaternary structure, can be very stable or else transient,
forming in order to transmit a signal.
In this lesson, you will learn that protein structure is stable,
but not very stable and you will learn that all information needed to fold
a protein into its stable structure is in the amino acid sequence.
Proteins fold up in roughly seconds to minutes,
but we calculate that to be much faster than they should be taking.
In order to fold into their stable structure,
many proteins require some help.
We will see that proteins have internal motions and that
proteins can be classified according to function and complexity.
Let's consider the protein folding and unfolding process.
On the left is a protein in water not folded and on the right,
you see some structure and this picture on the right,
reflects the folded protein.
In water, the unfolded protein has many different structures,
rapidly interchanging and on the right,
the folded protein, it's a structure that's relatively fixed.