Melanotropin Bioassays
Mac E. Hadley in The Melanotropic Peptides, 2018
The skin of the frog has been most widely used for the study of the melanotropic activity of peptides. Both in vitro and in vivo bioassays have been utilized. Both assays involve the response of integumental chromatophores to stimulation by melanotropins. This response to exogenous melanotropins is identical to that resulting from the release of endogenous melanotropins from the pars intermedia of the pituitary gland. Melanotropins stimulate the dispersion of melanosomes out into the dendritic processes of melanophores and concomitantly stimulate the aggregation of reflecting platelets within iridophores. The composite structural unit of color change is referred to as the “chromatophore unit” (see Bagnara, Volume II, Chapter 2).
Animal Source Foods
Chuong Pham-Huy, Bruno Pham Huy in Food and Lifestyle in Health and Disease, 2022
Coloration or pigmentation in animals mediates the relationship between an organism and its environment in important ways, including camouflage, mimicry, social signaling, antipredator defenses, parasitic exploitation, thermoregulation, and protection from ultraviolet light, microbes, and abrasion (5–6). Some aquatic animals such as fish, amphibians and cephalopods use pigmented chromatophores to provide camouflage. Pigmentation is used in signalization between animals, such as in courtship and sexual relation. For example, some cephalopods use their chromatophores to communicate. Across animals, coloration serves as a dynamic form of information (5–6).
The Modification Of Arginine
Roger L. Lundblad in Chemical Reagents for Protein Modification, 2020
Vallejos and co-workers39 have examined the modification of a photophosphorylation factor in Rhodospirillum rubrum chromatophore with either 2,3-butanedione or phenylglyoxal as shown in Figure 22. The reactions were performed in 0.050 M borate, pH 7.8 (25°C). Stoichiometry is not reported but it is not unreasonable to suggest that the two reagents react at the same site, in which case phenylglyoxal is more effective. These reactions were performed in the dark. When the reaction with 2,3-butanedione is performed in the light there is an approximately 25-fold increase in the rate of inactivation. These investigators discuss this in terms of a conformational change in the chromatophore but do not consider possible photosensitization as described above. Homyk and Bragg40 compared the effect of 2,3-butanedione and phenylglyoxal on the energy-independent transhydrogenase of Escherichia coli. The results of these experiments are shown in Figure 23. The reactions were performed in 0.050 M sodium borate, pH 7.8 at 22°C. Phenylglyoxal and 2,3-butanedione were of approximately equal effectiveness in reducing enzymatic activity. The insets show plots of the logarithm of the observed pseudo-first-order rate constants vs. the logarithm of the inhibitor concentration. In this type of analysis a straight line should be obtained with a slope equal to the number of inhibitor molecules reacting with each active site to yield an inactive enzyme.41,42 The analysis for phenylglyoxal yielded a slope of 1.1 while that for 2,3-butanedione gave a slope of 0.8. Therefore these experiments are consistent with the loss in catalytic activity resulting from the modification of one arginyl residue per active site of the enzyme. Also shown in Figure 23 is the protection by substrates and substrate analogs on the rate of inactivation by 2,3-butanedione.
Synthesis, X-ray diffraction analysis, quantum chemical studies and α-amylase inhibition of probenecid derived S-alkylphthalimide-oxadiazole-benzenesulfonamide hybrids
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2022
Bilal Ahmad Khan, Syeda Shamila Hamdani, Muhammad Naeem Ahmed, Shahid Hameed, Muhammad Ashfaq, Ahmed M. Shawky, Mahmoud A. A. Ibrahim, Peter A. Sidhom
Drug discovery is a continuous challenge and keeps fascinating the researchers worldwide continuously regardless of the time and efforts required. Heterocycles, specially oxadiazoles, have been very important in drug discovery due to their important role in medicines. The use and demand of oxadiazoles motifs in drugs are increasing continuously and can be seen from their increasing number of patents filed, up to increase in 100% in last 10 years from 2000 to 2008, still this number is increasing on1. Nowadays, a considerable amount of drugs in use possess oxadiazole moiety, a few examples are zibotentan2–3, used for curing cancer, raltegravir, an important antiretroviral drug against HIV, and ataluren, used for the treatment of cystic fibrosis4. Oxadiazole rings help in fulfilling the dream of drug discovery in multiple ways, acting as an important part of pharmacophore, which stimulates the binding of chromatophore to ligand5, as a linker to fix the proper position of the substituent in space6 and help in controlling the molecular properties7. The importance of oxadiazole is not limited to the medicinal field but is also equally important in the industrial zone as a thermal stabiliser for polymer synthesis and has found wide applications in optics8–10. Many discoveries have proved oxadiazole motif has a broad range of pharmaceutical importance as an antidiabetic11, lipoxygenase inhibitor12, anti-inflammation13, anti-infection14, elastase inhibitors15, amylase inhibitor16, antibacterial17, antiobesity18, nonpeptidic procollagen C-proteinase inhibition19, anticancer20, and dipeptidyl peptidase IV inhibition21. Moreover, oxadiazoles are also reported to inhibit monoamine oxidase22, niacin receptor (GPR109A) agonist23, larvicide24, antifungal25, and glutaminyl cyclase inhibitors26.
Related Knowledge Centers
- Biological Pigment
- Cell Signaling
- Eye Color
- Neural Crest
- Melanocyte
- Ectotherm
- Animal Embryonic Development
- Reflection
- Camouflage
- Hormone