biostudies-literatureKirpich JSUnited States Department of EnergyNational Science Foundation4839https://www.ebi.ac.uk/biostudies/studies/S-EPMC11084411biostudies-literatureUnknown25(9)The involvement of the second pair of chlorophylls, termed A_-1A and A_-1B, in light-induced electron transfer in photosystem I (PSI) is currently debated. Asparagines at PsaA600 and PsaB582 are involved in coordinating the A_-1B and A_-1A pigments, respectively. Here we have mutated these asparagine residues to methionine in two single mutants and a double mutant in PSI from <i>Synechocystis</i> sp. PCC 6803, which we term NA600M, NB582M, and NA600M/NB582M mutants. (P700⁺-P700) FTIR difference spectra (DS) at 293 K were obtained for the wild-type and the three mutant PSI samples. The wild-type and mutant FTIR DS differ considerably. This difference indicates that the observed changes in the (P700⁺-P700) FTIR DS cannot be due toInternational journal of molecular sciencesIs the A_-1 Pigment in Photosystem I Part of P700? A (P700⁺-P700) FTIR Difference Spectroscopy Study of A_-1 Mutants.PMC11084411DE-SC-0017937# 2313482Kirpich JSAgarwala NNelson MRLuo LHastings GXu WfalseIs the A_-1 Pigment in Photosystem I Part of P700? A (P700⁺-P700) FTIR Difference Spectroscopy Study of A_-1 Mutants.The involvement of the second pair of chlorophylls, termed A_-1A and A_-1B, in light-induced electron transfer in photosystem I (PSI) is currently debated. Asparagines at PsaA600 and PsaB582 are involved in coordinating the A_-1B and A_-1A pigments, respectively. Here we have mutated these asparagine residues to methionine in two single mutants and a double mutant in PSI from <i>Synechocystis</i> sp. PCC 6803, which we term NA600M, NB582M, and NA600M/NB582M mutants. (P700⁺-P700) FTIR difference spectra (DS) at 293 K were obtained for the wild-type and the three mutant PSI samples. The wild-type and mutant FTIR DS differ considerably. This difference indicates that the observed changes in the (P700⁺-P700) FTIR DS cannot be due to2024-01-01T00:00:00Z2024 Apr2026-04-24T03:13:57.499Z2026-04-24T03:09:32.982ZS-EPMC110844113873205610.3390/ijms25094839