Opposing Influences of Ruffling and Doming Deformation on the 4‐N Cavity Size of Porphyrin Macrocycles: The Role of Heme Deformations Revealed

Zhou, Zaichun; Shen, Min; Cao, Chenzhong; Liu, Qiuhua; Yan, Ziqiang

doi:10.1002/chem.201200722

Cited by 47 publications

(34 citation statements)

References 40 publications

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“…That the Soret band of Mb is affected in the native state too by some of the crowding agents presents an interesting phenomenon. Previous studies have ascribed red‐shifts (arising from hybrid orbital deformation effect) in the heme visible bands (as observed for D6) to the ruffling (non‐planarity) of this cofactor brought about by changes of protein structure in its immediate proximity [37–39]. This implies that D6 based on its high packing density perturbs native Mb in a manner that the heme pocket is distinctly altered, an aspect that can have several consequences on the manner in which Mb functions.…”

Section: Discussionmentioning

confidence: 92%

Unusual effects of crowders on heme retention in myoglobin

et al. 2015

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Edited by Stuart FergusonKeywords: Macromolecular crowder Glucose and sucrose Excluded volume effect Heme retention BSA Lysozyme Soft interaction a b s t r a c t Myoglobin (Mb) undergoes pronounced heme loss under denaturing conditions wherein the proximal histidine gets protonated. Our data show that macromolecular crowding agents (both synthetic and protein based) can appreciably influence the extent of heme retention in Mb. Interestingly, glucose and sucrose, the monomeric constituents of dextran and ficoll-based crowders were much more effective in preventing heme dissociation of Mb, albeit, at much higher concentrations. The protein crowders BSA and lysozyme show very interesting results with BSA bringing about the maximum heme retention amongst all the crowding agents used while lysozyme induced heme dissociation even in the native state of Mb. The stark difference that these protein crowders exhibit when interacting with the heme protein is a testament to the varied interaction potentials that a test protein might be exposed to in the physiological (crowded) milieu.

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Section: Discussionmentioning

confidence: 92%

Unusual effects of crowders on heme retention in myoglobin

et al. 2015

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“…A plausible explanation of the lower activation energy for this process in Zn‐S0 than in S0 can be explained in terms of the zinc metallation effect. Indeed, the porphyrin core of metallo‐porphyrins is known to display more distortion and deformation modes than their free‐base analogues (the latter most usually having a flatter structure than the former) in order to accommodate the metal ion into the cavity, which impacts on the Gibbs activation energies (Δ G ≠ ) of conformational processes, such as rotations 67–71. Similarly to S0 , the β‐pyrrolic proton signal of S1 splits from one (room temperature) into two distinct singlets at 203 K ( D 2 d → D 2 symmetry), which has also been attributed to the slowing down of the NH tautomerism process (Figure 8, right).…”

Section: Resultsmentioning

confidence: 99%

“…Indeed, the porphyrin core of metalloporphyrins is known to display more distortion and deformation modes than their free-base analogues (the latter most usually having a flatter structure than the former) in order to accommodate the metal ion into the cavity, which impacts on the Gibbs activation energies (DG°) of conformational processes, such as rotations. [67][68][69][70][71] Similarly to S0, the b-pyrrolic proton signal of S1 splits from one (room temperature) into two distinct singlets at 203 K (D 2d !D 2 symmetry), which has also been attributed to the slowing down of the NH tautomerism process (Figure 8, right). Also in this case, the signal of the b' protons is broader than that of the b'' protons (full width at half maximum, FWHM = 5.4 and 3.8 Hz, respectively), which is indicative of long-range couplings 4 J(N-H/b'-H) in the former.…”

Section: Variable-temperature Nmr Experimentsmentioning

confidence: 99%

Tautomerism and Atropisomerism in Free‐Base (meso)‐Strapped Porphyrins: Static and Dynamic Aspects

Urbani

Torres

2014

Chemistry A European J

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We report herein some outstanding examples of atropisomerism and tautomerism in five (meso-)strapped porphyrins. Porphyrins S0-S4 have been synthesised, characterised and studied in detail by spectroscopic and spectrometric techniques, and their isomeric purity verified by HPLC analysis. In particular, they exhibit perfectly well-defined NMR spectra that display distinct patterns depending on their average symmetry at room temperature: C2v , D2d , C2h , C2v , and D2h for S0-S4, respectively. NH tautomerism was evidenced by variable-low-temperature (1) H NMR experiments in [D2 ]dichloromethane performed on S0 (Δ${G{{{\ne}\hfill \atop {\rm 298K}\hfill}}}$=48±1 kJ mol(-1) ) and S1 (Δ${G{{{\ne}\hfill \atop {\rm 298K}\hfill}}}$=55±3 kJ mol(-1) ), which has led to an understanding of the average spectra observed for the five porphyrins at room temperature. On the other hand, S2 and S3 are stable atropisomers at room temperature, easily separated and characterised, as a result of restricted rotation of their strapped bridges due to their high rotational barrier energies. Upon heating to 82 °C, they slowly equilibrate to a thermodynamic ratio of 64:36 in favour of the more stable S2 isomer. This atropisomerisation process was evidenced by (1) H NMR spectroscopy and monitored by HPLC, from which high rotational energy barriers of 115.2 (Δ${G{{{\ne}\hfill \atop {\rm S2}\rightarrow {\rm S3}\hfill}}}$) and 116.9 kJ mol(-1) (Δ${G{{{\ne}\hfill \atop {\rm S2}\rightarrow {\rm S3}\hfill}}}$) were deduced.

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“…Under the constraint of these frozen atoms, the two tryptophans are kept a fixed distance from the heme consistent with the crystal structure, but allowed sufficient freedom for relaxation in the optimization process. The constraints also restrict the macrocyclic of the heme from becoming unduly distorted while allowing porphyrins to dome and ruffle in their excited states . The methodology described does not take into account the effects of entropy in

Δ G

and neglects the role of solvent.…”

Section: Methodsmentioning

confidence: 99%

Quantum chemical calculations of tryptophan → heme electron and excitation energy transfer rates in myoglobin

2017

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The development of optical multidimensional spectroscopic techniques has opened up new possibilities for the study of biological processes. Recently, ultrafast two‐dimensional ultraviolet spectroscopy experiments have determined the rates of tryptophan → heme electron transfer and excitation energy transfer for the two tryptophan residues in myoglobin (Consani et al., Science, 2013, 339, 1586). Here, we show that accurate prediction of these rates can be achieved using Marcus theory in conjunction with time‐dependent density functional theory. Key intermediate residues between the donor and acceptor are identified, and in particular the residues Val68 and Ile75 play a critical role in calculations of the electron coupling matrix elements. Our calculations demonstrate how small changes in structure can have a large effect on the rates, and show that the different rates of electron transfer are dictated by the distance between the heme and tryptophan residues, while for excitation energy transfer the orientation of the tryptophan residues relative to the heme is important. © 2017 The Authors. Journal of Computational Chemistry Published by Wiley Periodicals, Inc.

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Opposing Influences of Ruffling and Doming Deformation on the 4‐N Cavity Size of Porphyrin Macrocycles: The Role of Heme Deformations Revealed

Cited by 47 publications

References 40 publications

Unusual effects of crowders on heme retention in myoglobin

Unusual effects of crowders on heme retention in myoglobin

Tautomerism and Atropisomerism in Free‐Base (meso)‐Strapped Porphyrins: Static and Dynamic Aspects

Quantum chemical calculations of tryptophan → heme electron and excitation energy transfer rates in myoglobin

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