PMID- 32832056
OWN - NLM
STAT- PubMed-not-MEDLINE
LR  - 20220218
IS  - 2041-6520 (Print)
IS  - 2041-6539 (Electronic)
IS  - 2041-6520 (Linking)
VI  - 11
IP  - 23
DP  - 2020 Jun 21
TI  - The role of porphyrin peripheral substituents in determining the reactivities of 
      ferrous nitrosyl species.
PG  - 5909-5921
LID - 10.1039/d0sc01625j [doi]
AB  - Ferrous nitrosyl FeNO(7) species is an intermediate common to the catalytic 
      cycles of Cd(1)NiR and CcNiR, two heme-based nitrite reductases (NiR), and its 
      reactivity varies dramatically in these enzymes. The former reduces NO(2) (-) to 
      NO in the denitrification pathway while the latter reduces NO(2) (-) to NH(4) (+) 
      in a dissimilatory nitrite reduction. With very similar electron transfer 
      partners and heme based active sites, the origin of this difference in reactivity 
      has remained unexplained. Differences in the structure of the heme d (1) 
      (Cd(1)NiR), which bears electron-withdrawing groups and has saturated pyrroles, 
      relative to heme c (CcNiR) are often invoked to explain these reactivities. A 
      series of iron porphyrinoids, designed to model the electron-withdrawing 
      peripheral substitution as well as the saturation present in heme d (1) in 
      Cd(1)NiR, and their NO adducts were synthesized and their properties were 
      investigated. The data clearly show that the presence of electron-withdrawing 
      groups (EWGs) and saturated pyrroles together in a synthetic porphyrinoid 
      (FeDEsC) weakens the Fe-NO bond in FeNO(7) adducts along with decreasing the 
      bond dissociation free energies (BDFE(NH)) of the FeHNO(8) species. The EWG 
      raises the E degrees  of the FeNO(7/8) process, making the electron transfer (ET) 
      facile, but decreases the pK (a) of FeNO(8) species, making protonation (PT) 
      difficult, while saturation has the opposite effect. The weakening of the Fe-NO 
      bonding biases the FeNO(7) species of FeDEsC for NO dissociation, as in 
      Cd(1)NiR, which is otherwise set-up for a proton-coupled electron transfer (PCET) 
      to form an FeHNO(8) species eventually leading to its further reduction to 
      NH(4) (+).
CI  - This journal is (c) The Royal Society of Chemistry 2020.
FAU - Amanullah, Sk
AU  - Amanullah S
AUID- ORCID: 0000-0003-3288-5942
AD  - School of Chemical Sciences , Indian Association for the Cultivation of Science , 
      2A & 2B Raja SC Mullick Road , Kolkata , India - 700032 . Email: 
      icad@iacs.res.in.
FAU - Dey, Abhishek
AU  - Dey A
AUID- ORCID: 0000-0002-9166-3349
AD  - School of Chemical Sciences , Indian Association for the Cultivation of Science , 
      2A & 2B Raja SC Mullick Road , Kolkata , India - 700032 . Email: 
      icad@iacs.res.in.
LA  - eng
PT  - Journal Article
DEP - 20200507
PL  - England
TA  - Chem Sci
JT  - Chemical science
JID - 101545951
PMC - PMC7407271
EDAT- 2020/08/25 06:00
MHDA- 2020/08/25 06:01
PMCR- 2020/05/07
CRDT- 2020/08/25 06:00
PHST- 2020/03/19 00:00 [received]
PHST- 2020/05/07 00:00 [accepted]
PHST- 2020/08/25 06:00 [entrez]
PHST- 2020/08/25 06:00 [pubmed]
PHST- 2020/08/25 06:01 [medline]
PHST- 2020/05/07 00:00 [pmc-release]
AID - d0sc01625j [pii]
AID - 10.1039/d0sc01625j [doi]
PST - epublish
SO  - Chem Sci. 2020 May 7;11(23):5909-5921. doi: 10.1039/d0sc01625j. eCollection 2020 
      Jun 21.