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2D IR spectroscopy of histidine: probing side-chain structure and dynamics via backbone amide vibrations.

Ghosh A, Tucker MJ, Gai F - J Phys Chem B (2014)

Bottom Line: It is well known that histidine is involved in many biological functions due to the structural versatility of its side chain.However, probing the conformational transitions of histidine in proteins, especially those occurring on an ultrafast time scale, is difficult.Because of the intrinsic ultrafast time resolution of 2D IR spectroscopy, we believe that the current approach, when combined with the isotope editing techniques, will be useful in revealing the structural dynamics of key histidine residues in proteins that are important for function.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104-6323, United States.

ABSTRACT
It is well known that histidine is involved in many biological functions due to the structural versatility of its side chain. However, probing the conformational transitions of histidine in proteins, especially those occurring on an ultrafast time scale, is difficult. Herein we show, using a histidine dipeptide as a model, that it is possible to probe the tautomer and protonation status of a histidine residue by measuring the two-dimensional infrared (2D IR) spectrum of its amide I vibrational transition. Specifically, for the histidine dipeptide studied, the amide unit of the histidine gives rise to three spectrally resolvable amide I features at approximately 1630, 1644, and 1656 cm(-1), respectively, which, based on measurements at different pH values and frequency calculations, are assigned to a τ tautomer (1630 cm(-1) component) and a π tautomer with a hydrated (1644 cm(-1) component) or dehydrated (1656 cm(-1) component) amide. Because of the intrinsic ultrafast time resolution of 2D IR spectroscopy, we believe that the current approach, when combined with the isotope editing techniques, will be useful in revealing the structural dynamics of key histidine residues in proteins that are important for function.

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Normalized amide I′ bands of the histidine amide in theHis dipeptide measured at different pH values, as indicated. Shownin the inset is the structure of the dipeptide, where the histidineside chain is in its π tautomer form.
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fig1: Normalized amide I′ bands of the histidine amide in theHis dipeptide measured at different pH values, as indicated. Shownin the inset is the structure of the dipeptide, where the histidineside chain is in its π tautomer form.

Mentions: To test the utilityof the amide I vibrational mode of His as astructural and dynamical IR reporter of His tautomerization and protonationstatus in proteins, we performed linear and nonlinear IR measurementson an N-terminally acetylated and C-terminally methylamidated Hisamino acid (Figure 1). Because this model compoundcontains two backbone carbonyl groups, it is referred to here as Hisdipeptide. In addition, to isolate the amide I band of His, 13C-acetic anhydride was used to cap the N-terminus. In the followingtext, only results pertinent to the unlabeled His amide I band arediscussed.


2D IR spectroscopy of histidine: probing side-chain structure and dynamics via backbone amide vibrations.

Ghosh A, Tucker MJ, Gai F - J Phys Chem B (2014)

Normalized amide I′ bands of the histidine amide in theHis dipeptide measured at different pH values, as indicated. Shownin the inset is the structure of the dipeptide, where the histidineside chain is in its π tautomer form.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4317052&req=5

fig1: Normalized amide I′ bands of the histidine amide in theHis dipeptide measured at different pH values, as indicated. Shownin the inset is the structure of the dipeptide, where the histidineside chain is in its π tautomer form.
Mentions: To test the utilityof the amide I vibrational mode of His as astructural and dynamical IR reporter of His tautomerization and protonationstatus in proteins, we performed linear and nonlinear IR measurementson an N-terminally acetylated and C-terminally methylamidated Hisamino acid (Figure 1). Because this model compoundcontains two backbone carbonyl groups, it is referred to here as Hisdipeptide. In addition, to isolate the amide I band of His, 13C-acetic anhydride was used to cap the N-terminus. In the followingtext, only results pertinent to the unlabeled His amide I band arediscussed.

Bottom Line: It is well known that histidine is involved in many biological functions due to the structural versatility of its side chain.However, probing the conformational transitions of histidine in proteins, especially those occurring on an ultrafast time scale, is difficult.Because of the intrinsic ultrafast time resolution of 2D IR spectroscopy, we believe that the current approach, when combined with the isotope editing techniques, will be useful in revealing the structural dynamics of key histidine residues in proteins that are important for function.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, University of Pennsylvania , Philadelphia, Pennsylvania 19104-6323, United States.

ABSTRACT
It is well known that histidine is involved in many biological functions due to the structural versatility of its side chain. However, probing the conformational transitions of histidine in proteins, especially those occurring on an ultrafast time scale, is difficult. Herein we show, using a histidine dipeptide as a model, that it is possible to probe the tautomer and protonation status of a histidine residue by measuring the two-dimensional infrared (2D IR) spectrum of its amide I vibrational transition. Specifically, for the histidine dipeptide studied, the amide unit of the histidine gives rise to three spectrally resolvable amide I features at approximately 1630, 1644, and 1656 cm(-1), respectively, which, based on measurements at different pH values and frequency calculations, are assigned to a τ tautomer (1630 cm(-1) component) and a π tautomer with a hydrated (1644 cm(-1) component) or dehydrated (1656 cm(-1) component) amide. Because of the intrinsic ultrafast time resolution of 2D IR spectroscopy, we believe that the current approach, when combined with the isotope editing techniques, will be useful in revealing the structural dynamics of key histidine residues in proteins that are important for function.

Show MeSH
Related in: MedlinePlus