Structures of the fluorescent probe molecules: (a) coumarin 153 (C153), (b) the ammonium salt of 8-anilino-1-naphthalenesulfonic acid (1,8-ANS), (c) anilino-2-aminonaphthalene-6-dimethylsulfonamide (2,6-ANSDMA), and (d) -(N,N-dimethylamino)-6-naphthoyl-4-trans-cyclohexanoic acid (DANCA). The structures for ANSDMA and DANCA were incorrectly transmitted in Ref. 25.
(Color) A snapshot of equilibrated C153-apomyoglobin in water from molecular dynamics simulations using CHARMM22 force field. The C153 is shown in a space-filling model, and two histidine residues in the hemepocket are also shown with stick and ball models. His93 is the proximal histidine belonging to the F helix and is also referred to as HisF8. His64 is the distal histidine, and also referred to as HisE7.
Fluorescence upconversion traces obtained for C153 in apoMb at the indicated wavelengths. The maximum intensity of the traces are relative to the most intense, i.e., that at . The decays used to construct the time-resolved emission spectra were typically collected over a range of wavelengths from at intervals; a total of eight or nine decays was used to generate the time-resolved emission spectra, from which the were calculated.
Normalized time resolved emission spectra for C153 in (a) apoMb and (b) apoLba at and . Corresponding steady-state and “zero-time” spectra are included. Almost 60% of the solvation is complete in both systems within the time resolution of our instrument .
Comparison of for C153 in apoMb and apoLba obtained from fluorescence upconversion experiments with those obtained from molecular dynamics simulations. In both proteins, the initial fast component occurs within the time resolution of our instrument.
Solvation of C153 in two hemeproteins . Unless otherwise indicated, the parameter refers to that experimentally obtained. The time constants are in picoseconds and the frequencies and reorganization energies are given in wave numbers.
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