Anil J Patwardhan

US Patent:

20080081340, Apr 3, 2008

Filed:

Sep 29, 2006

Appl. No.:

11/529574

Inventors:

Anil Patwardhan - San Francisco CA, US
Handong Li - San Jose CA, US
Narayan Sundararajan - San Francisco CA, US

International Classification:

G01N 33/53
G01N 33/553
C12P 21/06
C12M 3/00

US Classification:

435 71, 4352872, 436526, 977902, 435 681

Abstract:

The sensitivity of surface enhanced Raman spectroscopy to silver nano-particle/peptide aggregates is increased by prior treatment of the peptides. According to a first type of embodiment, an enzyme such as Glu-C is used for protein(s) digestion based on the enzyme's ability to cleave proteins at a selected location having a negative charge, such as at aspartic acid and glutamic acid. This type of digestion is used to derive a higher proportion of positively charged component peptides sequences as compared to the component peptides sequences obtained by standard tryptic digestion of protein(s). According to a second type of embodiment, methyl-esterification of peptides suppresses the negative charge contributions of portions of the peptides such as aspartic acid, glutamic acid, and the C-terminus. Both types of embodiments result in increased binding affinity of the resulting component sequence peptides with negatively charged nano-particles such as silver nano-particles. According to yet other embodiments, the first and second types of embodiments can be combined for further sensitivity increase.