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A high pressure Raman study of 9-hydroxyphenalenone and pressure-induced phase transitions (1987)

Jayaraman, A. ; Kourouklis, G. A. ; Haddon, R. C.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 87 (1987), S. 3587-3590

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: The pressure effect on 9-hydroxyphenalenone (9-HPLN) has been investigated using Raman scattering and optical absorption techniques in a diamond anvil cell up to 70 kbar hydrostatic pressure. A pressure-induced first-order phase transition occurs near 6 kbar and the Raman data shows that the transition is to the same phase that is obtained on cooling 9-HPLN below 255 K at ambient pressure. The phase boundary has a positive slope with dT/dP=7 K/kbar. The Raman data indicate that there may be another phase change near 50 kbar. A strong and sharp Raman frequency near 12 cm−1 is observed in all the phases up to the highest pressure investigated. The weak pressure dependence of this frequency and its presence up to the highest pressure suggests that it may be a molecular mode rather than an external mode frequency. The optical absorption associated with π–π* excitation exhibits a large red shift, as expected of an aromatic molecular crystal.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.453004

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Is all cyclo(His-Pro) derived from thyrotropin-releasing hormone? (1987)

Prasad, Chandan ; Jayaraman, A. ; Robertson, Hugh J. F. ; [et al.]

Springer

Neurochemical research 12 (1987), S. 767-774

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ISSN: 1573-6903

Keywords: Cyclo(His-Pro) ; TRH

Source: Springer Online Journal Archives 1860-2000

Topics: Medicine

Notes: Abstract Cyclo(His-Pro), or histidyl-proline diketopiperazine, is an endogenous cyclic dipeptide that is ubiquitously distributed in tissues and body fluids of both man and animals. This cyclic dipeptide is not only structurally related to thyrotropin-releasing hormone (TRH, pGlu-His-ProNH2), but it can also arise from TRH by the action of the enzyme pyroglutamate amino-peptidase (pGlu-peptidase). The data on the distribution of TRH, cyclo(His-Pro), and pGlu-peptidase under normal and abnormal conditions are summarized and potential relationships analyzed. We conclude that all of the cyclo(His-Pro) cannot be derived from TRH. Two additional sources of cyclo(His-Pro) are suggested. It is proposed that 29,247 molecular weight TRH prohormone, prepro TRH, which contains 5 copies of TRH sequence, can be processed to yield cyclo(His-Pro). Thus, both TRH and cyclo(His-Pro) share a common precursor, prepro[TRH/Cyclo(His-Pro)].