Disclosed are compositions and methods for detecting small quantities of
analytes such as proteins and peptides. The method involves associating a primer
with an analyte and subsequently using the primer to mediate rolling circle replication
of a circular DNA molecule. Amplification of the DNA circle is dependent on the
presence of the primer. Thus, the disclosed method produces an amplified signal,
via rolling circle amplification, from any analyte of interest. The amplified DNA
remains associated with the analyte, via the primer, and so allows spatial detection
of the analyte. The disclosed method can be used to detect and analyze proteins
and peptides. Multiple proteins can be analyzed using microarrays to which the
various proteins are immobilized. A rolling circle replication primer is then associated
with the various proteins using a conjugate of the primer and a molecule that specifically
binds the proteins to be detectable. Rolling circle replication from the primers
results in production of a large amount of DNA at the sites in the array where
the proteins are immobilized. The amplified DNA serves as a readily detectable
signal for the proteins. The disclosed method can also be used to compare the proteins
expressed in two or more different samples. The information generated is analogous
to the type of information gathered in nucleic acid expression profiles. The disclosed
method allows sensitive and accurate detection and quantitation of proteins expressed
in any cell or tissue.
