Xanthomonas oryzae secretes a highly conserved sulfated peptide called Ax21, which mediates quorum sensing by controlling Xanthomonas motility, biofilm formation, and virulence.

TLS Online TPP Program

#Id: 2862

#Unit 13. Methods in Biology

RNA gives absorbance at 595 nm in presence of Diphenylamine while gives direct absorbance at 540 nm.

TLS Online TPP Program

#Id: 2863

#Unit 13. Methods in Biology

The electronic transitions of the peptide bond occur in the far UV. The intense peak at 190 nm, and the weaker one at 210–220 nm is due to the p ® p* and n ® p* transitions.

TLS Online TPP Program

#Id: 2864

#Unit 13. Methods in Biology

A number of amino acids (Asp, Glu, Asn, Gln, Arg and His) have weak electronic transitions at around 210 nm Usually, these cannot be observed in proteins because they are masked by the more intense peptide bond absorption.

TLS Online TPP Program

#Id: 2865

#Unit 13. Methods in Biology

The most useful range for proteins is above 230 nm, where there are absorptions from aromatic side chains.

TLS Online TPP Program

#Id: 2866

#Unit 13. Methods in Biology

A very weak absorption maximum of phenylalanine occurs at 257 nm, tyrosine and tryptophan dominate the typical protein spectrum with their absorption maxima at 274nm and 280 nm, respectively.

TLS Online TPP Program

#Id: 2867

#Unit 13. Methods in Biology

Cystine (Cys2) possesses a weak absorption maximum of similar strength as phenylalanine at 250 nm.