Issue 16, 2014

Magnetic field dependent long-lived spin states in amino acids and dipeptides

Abstract

Magnetic field dependence of long-lived spin states (LLSs) of the β-CH2 protons of aromatic amino acids was studied. LLSs are spin states, which are immune to dipolar relaxation, thus having lifetimes far exceeding the longitudinal relaxation times; the simplest example of an LLS is given by the singlet state of two coupled spins. LLSs were created by means of the photo-chemically induced dynamic nuclear polarization technique. The systems studied were amino acids, histidine and tyrosine, with different isotopomers. For labeled amino acids with the α-CH and aromatic protons substituted by deuterium at low fields the LLS lifetime, TLLS, for the β-CH2 protons was more than 40 times longer than the T1-relaxation time. Upon increasing the number of protons the ratio TLLS/T1 was reduced; however, even in the fully protonated amino acids it was about 10; that is, the long-lived mode was still preserved in the system. In addition, the effect of paramagnetic impurities on spin relaxation was studied; field dependencies of T1 and TLLS were measured. LLSs were also formed in tyrosine-containing dyads; a TLLS/T1 ratio of ∼7 was found, usable for extending the spin polarization lifetime in such systems.

Graphical abstract: Magnetic field dependent long-lived spin states in amino acids and dipeptides

Article information

Article type
Paper
Submitted
09 Dec 2013
Accepted
17 Feb 2014
First published
17 Feb 2014

Phys. Chem. Chem. Phys., 2014,16, 7584-7594

Magnetic field dependent long-lived spin states in amino acids and dipeptides

A. N. Pravdivtsev, A. V. Yurkovskaya, H. Zimmermann, H. Vieth and K. L. Ivanov, Phys. Chem. Chem. Phys., 2014, 16, 7584 DOI: 10.1039/C3CP55197K

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