Proton NMR relaxation studies of solid tyrosine derivatives and their mixtures with L-leucinamide.
Proton NMR relaxation time measurements were carried out on solid tyrosine derivatives: acetyl-L-tyrosine ethyl ester (Ac-Tyroet), N-carbobenzyloxy-L-tyrosine ethyl ester (CBZ-Tyroet), N-trifluoroacetyl-L-tyrosine ethyl ester (TFAc-Tyroet) and their mixtures with L-leucinamide. It was found that spin-lattice relaxation was driven mainly by methyl group rotation it low temperature for the pure solids and the mixtures. Benzene ring flipping motion and a third motion (possibly whole molecule tumbling) were found to be responsible for relaxing Ac-Tyroet and CBZ-Tyroet at high temperature. However, these motions were highly hindered in TFAc-Tyroet. Molecular tumbling motion was detected in the supercooled liquid mixtures of L-leuNH/CBZ-Tyroet and L-leuNH/Ac-Tyroet, while this motion is absent in the mixture L-leuNH/TFAc-Tyroet. The hindered motion in TFAc-Tyroet may be one of the factors affecting its ability to form a supercooled liquid with L-leucinamide.
Institute of Food Research, Norwich Laboratory, UK.
Y L
YL
Wang
P S
PS
Belton
H R
HR
Tang
D001554:Benzene; D006860:Hydrogen Bonding; D007930:Leucine / Q000031:analogs & derivatives* / Q000737:chemistry; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D019097:Spin Trapping; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry
C121091:N-carbobenzyloxytyrosine ethyl ester; D014443:Tyrosine; C007651:ethyl N-alpha-acetyl-tyrosinate; D007930:Leucine; D001554:Benzene; C013086:leucinamide