The interactions between cellular retinol-binding protein (CRBP-I) and retinal: A vibrational spectroscopic study

Abstract

Preresonance Raman difference spectra have been obtained for all‐trans retinal in dilute CCl4 solution, complexed with cellular retinol‐binding protein (CRBP‐I) and retinol‐binding protein (RBP). These spectra indicate that retinal is of a slightly more planar conformation within the binding pocket of CRBP‐I than in solution or hydrophobically complexed with RBP. Compared to retinal in solution or bound to RBP, the conformation of the polyene tail of the retinal chromophore is perturbed from C8 through C11. This perturbation is probably due to the close proximity of the Lys40 in the CRBP‐I binding pocket to the above‐mentioned carbons. The C(DOUBLE BOND)O stretching vibration of bound retinal carbonyl has been found to shift from 1664 cm−1 solubilized in CCl4 to 1650 and 1645 cm−1 in RBP and CRBP‐I, respectively, and significantly broadened in both cases. The frequency shift and broadening have been attributed to hydrogen bonding. These have been compared to calibrations of frequency shift (ΔνC(DOUBLE BOND)O) vs. ΔH and ΔG of all‐trans retinal complexed with a series of phenol derivatives of incremental proton‐donating ability as obtained by the relationship of van't Hoff. By this relationship, the binding enthalpy of the all‐trans retinal carbonyl moiety bound to CRBP‐I and RBP is −28.1 kJ/mol (−6.7 kcal/mol) and −23.5 kJ/mol (−5.6 kcal/mol), respectively. The free energy of binding of the retinal carbonyl bound to CRBP‐I and RBP has been determined to be −10.5 kJ/mol (−2.5 kcal/mol) and −7.2 kJ/mol (−1.7 kcal/mol), respectively. The hydrogen‐bonded C(DOUBLE BOND)O moiety of retinal complexed with CRBP‐I accounts for a substantial (25%) but not overriding amount of the binding energy of CRBP‐I for retinal, and it also accounts for the protein's preference for binding retinol. © 1997 John Wiley & Sons, Inc. Biospect 3: 131–142, 1997

Highly Active Copolymerization of Ethylene and N-Acetyl-O-(ω-Alkenyl)-l-Tyrosine Ethyl Esters Catalyzed by Titanium Complex

“…Bands at 2918, 2847, 1470, and 719 cm −1 were characters of linear polyethylene ( Figure 3 ). Fan reported that C=O vibration absorption of N -acetyl- O -(ω-alkenyl)- l -tyrosine ethyl ester was at 1760 cm −1 [ 28 ]; however, herein, the bands of C=O of the copolymer B moved toward the red area and became 1739 cm −1 [ 29 ]. In addition, bands at 3390 and 3112 cm −1 were attributed to N–H vibration absorption, indicating that molecular association took place.…”

Copolymerization of Ethylene and Vinyl Amino Acidic Ester Catalyzed by Titanium and Zirconium Complexes

“…Table 2) is presented in Figure 3B. , which contributed to the forming of hydrogen bonds among inter-and intra-of the copolymer chains [25]. In addition, the bands at 3332 cm Table 1) and ethylene/N-acetyl-O-(dec-9-enyl)-L-tyrosine ethyl ester copolymer (B, run 14 in Table 2).…”