Effects of fluorescent probe structure on the dynamics at cysteine-34 within bovine serum albumin: Evidence for probe-dependent modulation of the cybotactic region

We have prepared a series of bovine serum albumins (BSA) that have been sit e-selectively labeled at cysteine-34 with one of four different sulfhydryl- selective boron dipyrromethene difluoride (BODIPY) fluorescent probes (BODI PY FL IA, BODIPY FL C-1 IA, BODIPY 530/550 IA, and BODIPY 493/503 MB). We d etermine how the choice of extrinsic probe structure dictates the recovered BSA-BODIPY dynamics under thermal (10-80 degreesC) and chemical (0-5M guan idine hydrochloride) denaturation conditions. The results of these experime nts show that the global protein dynamics are sensed equally by each fluore scent probe: however, the probe itself influences the local probe dynamics within the cybotactic region that surrounds cysteine-34. Thus, it seems ina ppropriate to think of these extrinsic fluorescent probes as passive, nonpa rticipatory viewers of local protein dynamics. (C) 2001 John Wiley & Sons, Inc.