Standard Thermodynamic Functions of Tripeptides N

The heat capacities of tripeptides N-formyl-l-methionyl-l-leucyl-l-phenylalaninol (N-f-MLF-OH) and N-formyl-l-methionyl-l-leucyl-l-phenylalanine methyl ester (N-f-MLF-OMe) were measured by precision adiabatic vacuum calorimetry over the temperature range from T = (6 to 350) K. The tripeptides were stable over this temperature range, and no phase change, transformation, association, or thermal decomposition was observed. The standard thermodynamic functions: molar heat capacity C[subscript p,m], enthalpy H(T) – H(0), entropy S(T), and Gibbs energy G(T) – H(0) of peptides were calculated over the range from T = (0 to 350) K. The low-temperature (T ≤ 50 K) heat capacities dependencies were analyzed using the Debye’s and the multifractal theories. The standard entropies of formation of peptides at T = 298.15 K were calculated.National Institute for Biomedical Imaging and Bioengineering (U.S.) (Grant EB-003151)National Institute for Biomedical Imaging and Bioengineering (U.S.) (Grant EB-001960)National Institute for Biomedical Imaging and Bioengineering (U.S.) (Grant EB-002026)Ministry of Education and Science of the Russian Federation (Contract 14.B37.21.0799

Dynamic Nuclear Polarization of Oxygen-17

Oxygen-17-detected DNP NMR of a water/glycerol glass enabled an 80-fold enhancement of signal intensity at 82 K, using the biradical TOTAPOL. The >6000-fold savings in acquisition time enable [superscript 17]O–[superscript 1]H distance measurements and heteronuclear correlation experiments. These experiments are the initial demonstration of the feasibility of DNP NMR on quadrupolar [superscript 17]O.National Institute for Biomedical Imaging and Bioengineering (U.S.) (Award EB-001960)National Institute for Biomedical Imaging and Bioengineering (U.S.) (Award EB-002804)National Institute for Biomedical Imaging and Bioengineering (U.S.) (Award EB-001035)National Institute for Biomedical Imaging and Bioengineering (U.S.) (Award EB-002026