[Paleopsych] peptide hormones

[Steve Hovland]

Although it might be possible to control all the functions of the brain 
using only a handful of hormones and neurotransmitters, the body has 
developed instead a hierarchy of systems of considerably greater 
complexity. This is an artifact rather than a necessity, i.e., "it is what 
it is."  Peptides are long chains or polymers of amino acids, which are 
just small molecules with one positive end and one negative end. When they 
link, this electrostatic energy is converted into a chemical bond. 
 Peptides undergo secondary structure transformations in their free state, 
twisting around themselves to minimize surface tension, an important term 
in the total surface free energy. This flexibility enables a much larger 
variety of forms than could be derived from nucleic acid polymers due to 
their double-helix which significantly limits their conformational variety. 
In addition, since they are composed of amino acids, peptides can contain 
and position highly polar or reactive residues. These reactive portions are 
normally hydrophilic and as such as contained on the outer portion of the 
coiled peptide where they can act most effectively on other entities. These 
two facts make proteins ideal as structures for enzymes. The body can fine 
tune the structure and therefore the chemical activity of enzymes by 
changing the genetic coding which produces them; and proteins can alter 
genetic function by regulating its transcription, turning genes on and off, 
and by enzymatically inhibiting or promoting synthesis of other peptides 
coded by the DNA. Other peptides - the immunoglobins - are responsible for 
recognizing non-self material (antigens) such as invading microbes by 
protuberances on their outer surfaces, and as such are key to the function 
of the immune system.  Finally, and most obviously, proteins comprise a 
large proportion of the physical structure of the body, as collagen, 
clathin, etc. Some diseases are directly related to mutated forms of 
proteins, resulting from mutated genes; still others, such as mad-cow and 
Alzheimer's, result from improper folding of peptides to form in 
non-water-soluble protein deposits - amyloid - whose residues have their 
hydrophobic regions directed outward.	
http://dwb.unl.edu/Teacher/NSF/C10/C10Links/www.pharmcentral.com/peptide  
s.htm