Spectroscopic Studies of Some Aromatic Acids with a Heteroatom in the Side‐Chain

The high-resolution X-ray crystallographic structures of horse heart azidometmyoglobin complexes of the wild-type protein and the His-64 → Thr variant have been determined to 2.0 and 1.8 Å respectively. Azide binds to wild-type metmyoglobin in a bent configuration with an Fe–N-1–N-3 angle of 119° and is oriented into the distal crevice in the direction of Ile-107. The proximity of the His-64 NE2 atom to the N-1 atom of the bound azide indicates stabilization of the ligand by the His-64 side chain through hydrogen bonding. In addition, structural characterization of wild-type horse heart azidometmyoglobin establishes that the only structural change induced by ligand binding is a small movement of the Leu-29 side chain away from the azide ligand. EPR and Fourier transform infrared spectroscopy were used to characterize the myoglobin azide complexes further. EPR spectroscopy revealed that, in contrast with wild-type azidometmyoglobin, two slightly different low-spin species are formed by azide bound to the His-64 → Thr variant both in solution and in a polycrystalline sample. One of these low-spin species has a greater relative intensity, with gvalues very similar to those of the azide complex of the wild-type protein. These EPR results together with structural information on this variant indicate the presence of two distinct conformations of bound azide, with one form predominating. The major conformation is comparable to that formed by wild-type myoglobin in which azide is oriented into the distal crevice. In the minor conformation the azide is oriented towards the exterior of the protein.

Download Full-text

Spectroscopic Studies of Surfactant Solubility. III. Side-chain Effects of Phosphatidyl Compounds in Chloroform Solutions

Bulletin of the Chemical Society of Japan ◽

10.1246/bcsj.54.2399 ◽

1981 ◽

Vol 54 (8) ◽

pp. 2399-2407 ◽

Cited By ~ 4

Author(s):

Mitsuyo Okazaki ◽

Ichiro Hara ◽

Yumiko K. Tsutsui ◽

Tsunetake Fujiyama

Keyword(s):

Spectroscopic Studies ◽

Side Chain

Download Full-text

Oxidative Oligomerization of DBL Catechol, a potential Cytotoxic Compound for Melanocytes, Reveals the Occurrence of Novel Ionic Diels-Alder Type Additions

International Journal of Molecular Sciences ◽

10.3390/ijms21186774 ◽

2020 ◽

Vol 21 (18) ◽

pp. 6774

Author(s):

Manickam Sugumaran ◽

Kubra Umit ◽

Jason Evans ◽

Rachel Muriph ◽

Shosuke Ito ◽

...

Keyword(s):

Spectroscopic Studies ◽

Diels Alder ◽

Oxidation Products ◽

Side Chain ◽

Liquid Chromatography Mass Spectrometry ◽

Carbonyl Derivative ◽

Cytotoxic Compound ◽

Whitening Agent ◽

Uv Visible ◽

Oxidation Chemistry

The exposure of human skin to 4-(4-hydroxyphenyl)-2-butanone (raspberry ketone, RK) is known to cause chemical/occupational leukoderma. RK is a carbonyl derivative of 4-(4-hydroxyphenyl)-2-butanol (rhododendrol), a skin whitening agent that was found to cause leukoderma in skin of many consumers. These two phenolic compounds are oxidized by tyrosinase and the resultant products seem to cause cytotoxicity to melanocytes by producing reactive oxygen species and depleting cellular thiols through o-quinone oxidation products. Therefore, it is important to understand the biochemical mechanism of the oxidative transformation of these compounds. Earlier studies indicate that RK is initially oxidized to RK quinone by tyrosinase and subsequently converted to a side chain desaturated catechol called 3,4-dihydroxybenzalacetone (DBL catechol). In the present study, we report the oxidation chemistry of DBL catechol. Using UV–visible spectroscopic studies and liquid chromatography mass spectrometry, we have examined the reaction of DBL catechol with tyrosinase and sodium periodate. Our results indicate that DBL quinone formed in the reaction is extremely reactive and undergoes facile dimerization and trimerization reactions to produce multiple isomeric products by novel ionic Diels-Alder type condensation reactions. The production of a wide variety of complex quinonoid products from such reactions would be potentially more toxic to cells by causing not only oxidative stress, but also melanotoxicity through exhibiting reactions with cellular macromolecules and thiols.

Download Full-text

Coordination structures of Mg2+and Ca2+in three types of tobacco calmodulins in solution: Fourier-transform infrared spectroscopic studies of side-chain COO−groups

Biopolymers ◽

10.1002/bip.22203 ◽

2013 ◽

Vol 99 (7) ◽

pp. 472-483 ◽

Cited By ~ 2

Author(s):

Nanao Suzuki ◽

Lica Fabiana Imai ◽

Yusuke Kato ◽

Koji Nagata ◽

Yuko Ohashi ◽

...

Keyword(s):

Fourier Transform ◽

Fourier Transform Infrared ◽

Spectroscopic Studies ◽

Side Chain ◽

Infrared Spectroscopic

Download Full-text

Vibrational Spectroscopic Studies on Fibrinogen Adsorption at Polystyrene/Protein Solution Interfaces: Hydrophobic Side Chain and Secondary Structure Changes

The Journal of Physical Chemistry B ◽

10.1021/jp0534683 ◽

2006 ◽

Vol 110 (10) ◽

pp. 5017-5024 ◽

Cited By ~ 42

Author(s):

Jie Wang ◽

Xiaoyun Chen ◽

Matthew L. Clarke ◽

Zhan Chen

Keyword(s):

Secondary Structure ◽

Spectroscopic Studies ◽

Side Chain ◽

Protein Solution ◽

Structure Changes ◽

Fibrinogen Adsorption

Download Full-text

The Isolation and Synthesis of E-24-Ethylidene-5α-lanost-8-en-3β-yl Acetate

Canadian Journal of Chemistry ◽

10.1139/v75-462 ◽

1975 ◽

Vol 53 (21) ◽

pp. 3247-3249 ◽

Cited By ~ 12

Author(s):

S. Safe ◽

L. M. Safe

Keyword(s):

Spectroscopic Studies ◽

Side Chain

Extraction of the fungus Mucorrouxii gave small amounts of a 32 carbon triterpene (M+ 454). Spectroscopic studies suggested a lanosterol ring skeleton with a 24-ethylidene group introduced into the side chain. The structure was confirmed by synthesis and shown to be E-24-ethylidene-5α-lanost-8-en-3β-yl acetate.

Download Full-text

Organic Curing Agents for Polysulfide Sealants. III. A Mechanistic Interpretation of the Thermal Degradation of Nitrile Oxide-Cured Polysulfide Sealants

Australian Journal of Chemistry ◽

10.1071/ch9900109 ◽

1990 ◽

Vol 43 (1) ◽

pp. 109 ◽

Cited By ~ 2

Author(s):

BC Ennis ◽

PJ Hanhela ◽

DB Paul

Keyword(s):

Thermal Analysis ◽

Acid Group ◽

Spectroscopic Studies ◽

Nitrile Oxide ◽

Side Chain ◽

Polymer Backbone ◽

Nitrile Oxides ◽

Liquid Polymers ◽

Curing Agents ◽

Group B

Sealants obtained by cure of polysulfide liquid polymers with aryl bis ( nitrile oxides) possess the thiohydroximic acid ester structural feature. Unexpectedly these materials were found to exhibit poor thermal stability: when heated at 60° they soften within days and liquefy in 3 weeks. Products obtained with excess nitrile oxide degraded faster than those produced with equimolar amounts of reagents. Interpretations considered included (A) dissociation of the thiohydroximic acid group, (B) reaction between nitrile oxide and a reactive centre in the polysulfide structure, and (c) addition of nitrile oxide to the side chain. It was shown that neither of the first two possibilities was applicable. Moreover, spectroscopic studies demonstrated that, after an initial rapid addition between nitrile oxide and thiol , a second slower reaction occurred which consumed additional nitrile oxide. Although aldehyde oximes and a- chloro oximes do not participate in such processes unless catalysts are present, thiohydroximic acid derivatives were shown to react with nitrile oxides at ambient temperature to form 1,2,4-oxadiazole 4-oxides and alkyl thiol . For the case of a polysulfide sealant the equivalent rupture of a C-S bond to form the thiol involves cleavage of the polymer backbone. Continuation of the process would lead to degradation of the sealant. These observations were supported by thermal analysis studies on the polysulfide sealants and model polymers.

Download Full-text

Synthesis and protonation studies of a meso-unsubstituted surfactant porphyrin

Canadian Journal of Chemistry ◽

10.1139/v85-400 ◽

1985 ◽

Vol 63 (9) ◽

pp. 2420-2424 ◽

Cited By ~ 3

Author(s):

Michel Ringuet ◽

Jacques Gagnon

Keyword(s):

Chloroform Solution ◽

Spectroscopic Studies ◽

Side Chain ◽

Carboxyl Groups ◽

Free Base ◽

Base Form

A meso-unsubstituted surfactant porphyrin has been synthesized. Spectroscopic studies show that intermolecular protonation occurs between the side-chain carboxyl groups and the inner nitrogen atoms of the porphyrin, leading to the formation of a porphyrin dication. In 5 × 10−5 M chloroform solution, 27% of the porphyrin molecules are in the dicationic form and they are self-associated with some remaining molecules in the free base form.

Download Full-text

Resonance Raman-spectroscopic studies of the hapten features involved in the binding of 2,4-dinitrophenyl haptens by the mouse myeloma proteins MOPC 315 and MOPC 460

Biochemical Journal ◽

10.1042/bj1750727 ◽

1978 ◽

Vol 175 (2) ◽

pp. 727-735 ◽

Cited By ~ 8

Author(s):

K Kumar ◽

D J Phelps ◽

P R Carey ◽

N M Young

Keyword(s):

Binding Sites ◽

Resonance Raman Spectroscopy ◽

Resonance Raman ◽

Immunoglobulin A ◽

Spectroscopic Studies ◽

Side Chain ◽

Raman Spectroscopic ◽

Myeloma Proteins ◽

Resonance Raman Spectra ◽

Mouse Myeloma

The binding of four dinitrophenyl haptens to the mouse myeloma proteins MOPC 315 IgA (immunoglobulin A) and MOPC 460IgA was studied by resonance Raman spectroscopy. Isotopic substitution with 15N and 2H was used to assign features in the resonance Raman spectra of the free haptens. Changes in each of these features on binding to the proteins could then be attributed to interactions of the proteins' binding sites with either the p-NO2 or the o-NO2/amine regions of the haptens. The interactions between a given hapten and MOPC 315 IgA are often quite distinct from those between the same hapten and MOPC 460 IgA. Moreover, for both antibodies the nature of the R side chain in a Dnp-NHR (Dnp, 2,4-dinitrophenyl) compound appears to modify the interactions between the Dnp chromophore and the protein. Thus, with the haptens studied, there is no unique set of contacts between the Dnp group and the binding site. The contacts expected between epsilon-2,4-dinitrophenyl-L-lysine and the site on MOPC 315 IgA, on the basis of a recent model for this site [Dwek, Wain-Hobson, Dower, Gettins, Sutton, Perkins & Givol (1977) Nature (London) 266, 31–37] were not detected. However, the contacts between this hapten and the site on MOPC 460 IgA were closer to those predicted by the model for MOPC 315 IgA.

Download Full-text