Low-frequency (50-440 cm(-1)) near-infrared-excitation resonance Raman (RR) spectra are reported for photosynthetic reaction centers (RCs) from the (M)H202L mutant of Rhodobacter sphaeroides. In this mutant, the histidine residue which ligates the M-side bacteriochlorophyll (BCh) of the special pair primary donor (P) of wild-type RCs is replaced by a noncoordinating leucine, resulting in the formation of a heterodimer primary donor (D) in which a bacteriopheophytin (BPh) replaces the M-side BCh. The RR data for the (M)H202L mutant RCs were acquired with excitation wavelengths which span the near-infrared absorption band of D and the a, absorption bands of the accessory BChs. For comparison, spectra were also acquired for wild-type RCs at the same excitation wavelengths.