how can i determin protein concentration using tha amide bond
absorbtion at 220nm. what is the absorbation coeffiecent at this
weavelength?

After searching the web over I realized this is not an easy task. The
extinction coefficient at a wavelength of 280 is unique for each
protein and depends on the amount of tyrosine, tryptophan and cystine
residues in the protein. The assumption is the spectral contributions
of these amino acids at 280 nm do not differ significantly in the
native form of the protein, relative to the denatured form. The
following url is a short discussion of how to calculate the extinction
coefficient of a protein if you know the number of those three amino
acids in the protein.

http://www.basic.nwu.edu/biotools/proteincalc.html#helpexco

However in further searching I found a url that quotes a Methods in
Enzymology article. In this article they talk about calculating the
extinction coefficient at 205 nm. The url is below. They reference the
articles they got the calculations from. It seems easy enough if you
have a UV spectrophotometer, quartz cuvettes, and some Brij 35. There
are some errors in your coefficient if your protein has a lot of
phenylalanine in it.

http://www.ruf.rice.edu/~bioslabs/methods/protein/absext.html

Hope that helps.
Nealc-ga

As far as I understand, protein concentration is determined by
measuring tyrosine residues at 280 nm, while determination of amide
bonds at 220 nm is used to investigate structural changes in the
protein backbone.

What I feel is about concentration of protein quantitatively can be
determined using TNBSA titration method. That can give better and more
correct value of concentrations.