Simple method to introduce an ester infrared probe into proteins.
The ester carbonyl stretching vibration has recently been shown to be a sensitive and convenient infrared (IR) probe of protein electrostatics due to the linear dependence of its frequency on local electric field. While an ester moiety can be easily incorporated into peptides via solid-phase synthesis, currently there is no method available to site-specifically incorporate it into a large protein. Herein, we show that it is possible to use a cysteine alkylation reaction to achieve this goal and demonstrate the feasibility of this simple method by successfully incorporating a methyl ester group (CH2COOCH3) into a model peptide (YGGCGG), two amyloid-forming peptides derived from the insulin B chain and Aβ, and bovine serum albumin (BSA). IR results obtained with those peptide and protein systems further confirm the utility of this vibrational probe in monitoring, for example, the structural integrity of amyloid fibrils and ligand binding-induced changes in protein local hydration status.
Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania, 19104.
Ismail A
IA
Ahmed
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania, 19104.
Feng
F
Gai
D016229:Amyloid beta-Peptides / Q000737:chemistry*; D000818:Animals; D002417:Cattle; D006801:Humans; D007328:Insulin / Q000737:chemistry*; D015335:Molecular Probes / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods
D016229:Amyloid beta-Peptides; D007328:Insulin; D015335:Molecular Probes; D012710:Serum Albumin, Bovine
amyloid; bovine serum albumin; cysteine alkylation; infrared probe; protein hydration; protein modification