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At least 163 records · Page 9Linked to original sources
PubMed2003

Eucalyptus globulus (camphor oil) against the zoonotic scabies, Sarcoptes scabiei.

In Egypt, Scarcoptes scabiei is the most prevalence mites of medical importance infesting man. This is true in overcrowded and poorly hygienic areas. Many effective acaridical regimens are available, but being compounds used as insecticides. With the success of camphor oil in treated human demodicidosis, it was applied for treating human scabies. Camphor oil with or without glycerol dilutions gave complete cure, with concentrations (100%, 75% and 50%) within five to ten days.

Adolescent↗
PubMed2003

[Camphor in the Edo era (4) moth repellent, deodorant, and fungicide].

A troublesome task in the daily life of the Edo era was ridding houses of harmful insects such as mosquitoes, fleas and clothes moths. People commonly drove away mosquitoes by making smoke. They hung their clothes or books in the air to keep them free from moisture. This was effective in protecting them from becoming moldy or being damaged by insects. Various medicinal plants were used to eliminate harmful house insects or agricultural vermin. Camphor was a variety of insecticide, but it was not popular in early Edo times because it was not easily available then. But in the end of Edo period, camphor became popular as a moth repellent.

Camphor↗
PubMed1983

Chronic camphor ingestion mimicking Reye's syndrome.

Camphor is a potentially dangerous drug which nevertheless remains popular as a home remedy. Because of its hepatoneurotoxic effects, camphor toxicity may clinically mimic Reye's syndrome. The differentiation between the two requires histologic examination of liver tissue, further emphasizing the need for a liver biopsy to establish the diagnosis of Reye's syndrome.

Biopsy↗
PubMed2004

Crystal structure of P450cin in a complex with its substrate, 1,8-cineole, a close structural homologue to D-camphor, the substrate for P450cam.

Cytochrome P450cin catalyzes the monooxygenation of 1,8-cineole, which is structurally very similar to d-camphor, the substrate for the most thoroughly investigated cytochrome P450, cytochrome P450cam. Both 1,8-cineole and d-camphor are C(10) monoterpenes containing a single oxygen atom with very similar molecular volumes. The cytochrome P450cin-substrate complex crystal structure has been solved to 1.7 A resolution and compared with that of cytochrome P450cam. Despite the similarity in substrates, the active site of cytochrome P450cin is substantially different from that of cytochrome P450cam in that the B' helix, essential for substrate binding in many cytochrome P450s including cytochrome P450cam, is replaced by an ordered loop that results in substantial changes in active site topography. In addition, cytochrome P450cin does not have the conserved threonine, Thr252 in cytochrome P450cam, which is generally considered as an integral part of the proton shuttle machinery required for oxygen activation. Instead, the analogous residue in cytochrome P450cin is Asn242, which provides the only direct protein H-bonding interaction with the substrate. Cytochrome P450cin uses a flavodoxin-like redox partner to reduce the heme iron rather than the more traditional ferredoxin-like Fe(2)S(2) redox partner used by cytochrome P450cam and many other bacterial P450s. It thus might be expected that the redox partner docking site of cytochrome P450cin would resemble that of cytochrome P450BM3, which also uses a flavodoxin-like redox partner. Nevertheless, the putative docking site topography more closely resembles cytochrome P450cam than cytochrome P450BM3.

Crystallography, X-Ray↗
PubMed2002

A Highly diastereoselective synthesis of (1R)-(+)-camphor-based chiral allenes and their asymmetric hydroboration-oxidation reactions.

Synthesis of camphor derived chiral allenes and their hydroboration-oxidation reactions are described. Reaction of (1R)-(+)-camphor with alkynyllithium followed by the reduction of the resulted propargyl alcohol derivatives using AlH3 furnished chiral allenes 2a-g in excellent yields with high diastereoselectivity. Reduction of the propargyl alcohols with aluminum hydride proceeded through selective intermolecular anti-addition of hydride ion. The stereochemistry of the chiral allenes 2 was assigned based on lanthanide shift studies and chemical correlations. Diastereoselectivity was observed in the hydroboration-oxidation of 2 which produced a mixture of (E,R) and (E,S) stereoisomers in a ratio of 6:1 to 18:1.

Journal Article↗
PubMed1999

Highly Diastereoselective Aldol Reactions with Camphor-Based Acetate Enolate Equivalents.

New lithium enolates of alpha-hydroxy ketones, derived from camphor, are evaluated for asymmetric aldol reactions in the presence of lithium chloride. The diastereoselectivity of the reactions between the lithium enolate of 3 and a variety of achiral aldehydes is strongly influenced by the lithium chloride salt. In these instances, the achieved levels of asymmetric induction, typically 95:5 dr, are in the range of those attained in aldol reactions involving the lithium enolate of the methyl ketone 4, which is sterically more demanding. The resulting aldol adducts are easily transformed into beta-hydroxy carboxylic acids, ketones, and aldehydes with concomitant recovery of the camphor, the chiral controller of the process, which can be reused.

Journal Article↗
PubMed2005

Synchronized sailing of two camphor boats in polygonal chambers.

The synchronized self-motion of two camphor boats on polygonal water chambers was investigated. The two boats synchronously moved depending on the number of corners in the polygon by changing the distance between the two boats through the corners. We regard the self-motion of a camphor boat as an oscillator; i.e., one cycle on the polygonal chamber corresponds to 2pi. Phase-locked synchronization at a phase difference of 2pi/3, which corresponds to the length of one side of the chamber, was observed with a triangular chamber. Two types of synchronized motion at phase differences of pi/2 and pi, which correspond to the length of one and two sides of the chamber, respectively, were observed with a square chamber. These characteristic features of synchronized self-motion were qualitatively reproduced by a numerical calculation that regarded the surface tension as the driving force and the number of corners in the chamber as a velocity-regulating mechanism. We believe that the present system may be a simple model of synchronization which depends on the geometry of the system.

Journal Article↗
PubMed2005

Characteristic self-motion of a camphor boat sensitive to ester vapor.

As a simple example of an autonomous motor, the self-motion of a camphor boat on water with changes in chemical stimuli was investigated. The nature of the self-motion of a camphor boat changed characteristically with the addition of ester vapor (methyl n-butyrate) to a circular water chamber. Thus, continuous motion changed to oscillatory motion, and its period increased depending on the location between an ester droplet and the chamber, L. The surface tension in the water chamber was measured to clarify how the velocity of the self-motion changed with L. The nature of the self-motion is discussed in relation to the surface tension as the driving force. We believe that the present results may be useful for realizing artificial chemotaxis systems under nonlinear and isothermal conditions.

Journal Article↗
PubMed2002

The 2-A crystal structure of 6-oxo camphor hydrolase. New structural diversity in the crotonase superfamily.

6-Oxo camphor hydrolase (OCH) is an enzyme of the crotonase superfamily that catalyzes carbon-carbon bond cleavage in bicyclic beta-diketones via a retro-Claisen reaction (Grogan, G., Roberts, G. A., Bougioukou, D., Turner, N. J., and Flitsch, S. L. (2001) J. Biol. Chem. 276, 12565-12572). The native structure of OCH has been solved at 2.0-A resolution with selenomethionine multiple wave anomalous dispersion and refined to a final R(free) of 19.0. The structure of OCH consists of a dimer of trimers that resembles the "parent" enzyme of the superfamily, enoyl-CoA hydratase. In contrast to enoyl-CoA hydratase, however, two octahedrally coordinated sodium atoms are found at the 3-fold axis of the hexamer of OCH, and the C-terminal helix of OCH does not form a discrete domain. Models of the substrate, 6-oxo camphor, and a proposed enolate intermediate in the putative active site suggest possible mechanistic roles for Glu-244, Asp-154, His-122, His-45, and His-145.

Amino Acid Sequence↗
PubMed2004

Structure of 6-oxo camphor hydrolase H122A mutant bound to its natural product, (2S,4S)-alpha-campholinic acid: mutant structure suggests an atypical mode of transition state binding for a crotonase homolog.

The crotonase homolog, 6-oxo camphor hydrolase (OCH), catalyzes the desymmetrization of bicyclic beta-diketones to optically active keto acids via an enzymatic retro-Claisen reaction, resulting in the cleavage of a carbon-carbon bond. We have previously reported the structure of OCH (Whittingham, J. L., Turkenburg, J. P., Verma, C. S., Walsh, M. A., and Grogan, G. (2003) J. Biol. Chem. 278, 1744-1750), which suggested the involvement of five residues, His-45, His-122, His-145, Asp-154, and Glu-244, in catalysis. Here we report mutation studies on OCH that reveal that H145A and D154N mutants of OCH have greatly reduced values of k(cat)/K(m) derived from a very large increase in K(m) for the native substrate, 6-oxo camphor. In addition, H122A has a greatly reduced value of k(cat), and its K(m) is five times that of the wild-type. The location of the active site is confirmed by the 1.9-A structure of the H122A mutant of OCH complexed with the minor diastereoisomer of (2S,4S)-alpha-campholinic acid, the natural product of the enzyme. This shows the pendant acetate of the product hydrogen bonded to a His-145/Asp-154 dyad and the endocyclic carbonyl of the cyclopentane ring hydrogen bonded to Trp-40. The results are suggestive of a base-catalyzed mechanism of C-C bond cleavage and provide clues to the origin of prochiral selectivity by the enzyme and to the recruitment of the crotonase fold for alternate modes of transition state stabilization to those described for other crotonase superfamily members.

Base Sequence↗
PubMed1987

Metabolism of Monoterpenes : Metabolic Fate of (+)-Camphor in Sage (Salvia officinalis).

The bicyclic monoterpene ketone (+)-camphor undergoes lactonization to 1,2-campholide in mature sage (Salvia officinalis L.) leaves followed by conversion to the beta-d-glucoside-6-O-glucose ester of the corresponding hydroxy acid (1-carboxymethyl-3-hydroxy-2,2,3-trimethyl cyclopentane). Analysis of the disposition of (+)-[G-(3)H]camphor applied to midstem leaves of intact flowering plants allowed the kinetics of synthesis of the bis-glucose derivative and its transport from leaf to root to be determined, and gave strong indication that the transport derivative was subsequently metabolized in the root. Root extracts were shown to possess beta-glucosidase and acyl glucose esterase activities, and studies with (+)-1,2[U-(14)C]campholide as substrate, using excised root segments, revealed that the terpenoid was converted to lipid materials. Localization studies confirmed the radiolabeled lipids to reside in the membranous fractions of root extracts, and analysis of this material indicated the presence of labeled phytosterols and labeled fatty acids (C(14) to C(20)) of acyl lipids. Although it was not possible to detail the metabolic steps between 1,2-campholide and the acyl lipids and phytosterols derived therefrom because of the lack of readily detectable intermediates, it seemed likely that the monoterpene lactone was degraded to acetyl CoA which was reincorporated into root membrane components via standard acyl lipid and isoprenoid biosynthetic pathways. Monoterpene catabolism thus appears to represent a salvage mechanism for recycling mobile carbon from senescing oil glands on the leaves to the roots.

Journal Article↗
PubMed2003

(1R,3S)-Camphoric acid as a building block in supramolecular chemistry: adducts with organic polyamines.

(1R,3S)-Camphoric acid [(1R,3S)-1,2,2,-trimethylcyclopentane-1,3-dicarboxylic acid, C(10)H(16)O(4)] forms adducts with a range of amines in which the acid component may be the neutral molecule, the mono-anion (C(10)H(15)O(4))(-) or the di-anion (C(10)H(14)O(4))(2-). The structures generated by the hard hydrogen bonds take the form of chains in the 1:1 adducts (II) and (III) formed with 4,4'-bipyridyl and 1,2-bis(4-pyridyl)ethane. There are single sheets in the hydrated 1:1 adduct (IV) formed with 1,4-diazabicyclo[2.2.2]octane, and pairwise-interwoven sheets in the 2:1 adduct (V) formed with hexamethylenetetramine. Three-dimensional frameworks are present in the salt-like 1:1 adduct (VI) formed with piperazine and in the hydrated 3:1 adduct (VII) formed with N,N'-dimethylpiperazine. This latter adduct contains both neutral C(10)H(16)O(4) and anionic (C(10)H(15)O(4))(-) units. In (II), (III) and (IV), the chain and sheet substructures are linked by C-H...O hydrogen bonds to form three-dimensional frameworks. The monoclinic polymorph of camphoric acid itself (I) has been reinvestigated.

Journal Article↗
PubMed1983

Regiochemistry of Camphor Analog Oxidation by Pseudomonas putida.

Pseudomonas putida cooxidized norcamphor and pericyclocamphanone to hydroxylated and lactonized products during growth on camphor. Norcamphor was hydroxylated at the 5 position, similar to the corresponding process in camphor, but pericyclocamphanone was oxidized at the 6 position. We conclude that the regiochemistry of the hydroxylation may be substrate controlled.

Journal Article↗
PubMed2001

Hydroxylation of camphor by reduced oxy-cytochrome P450cam: mechanistic implications of EPR and ENDOR studies of catalytic intermediates in native and mutant enzymes.

We have employed gamma-irradiation at cryogenic temperatures (77 K and also approximately 6 K) of the ternary complexes of camphor, dioxygen, and ferro-cytochrome P450cam to inject the "second" electron of the catalytic process. We have used EPR and ENDOR spectroscopies to characterize the primary product of reduction as well as subsequent states created by annealing reduced oxyP450, both the WT enzyme and the D251N and T252A mutants, at progressively higher temperatures. (i) The primary product upon reduction of oxyP450 4 is the end-on, "H-bonded peroxo" intermediate 5A. (ii) This converts even at cryogenic temperatures to the hydroperoxo-ferriheme species, 5B, in a step that is sensitive to these mutations. Yields of 5B are as high as 40%. (iii) In WT and D251N P450s, brief annealing in a narrow temperature range around 200 K causes 5B to convert to a product state, 7A, in which the product 5-exo-hydroxycamphor is coordinated to the ferriheme in a nonequilibrium configuration. Chemical and EPR quantitations indicate the reaction pathway involving 5B yields 5-exo-hydroxycamphor quantitatively. Analogous (but less extensive) results are seen for the alternate substrate, adamantane. (iv) Although the T252A mutation does not interfere with the formation of 5B, the cryoreduced oxyT252A does not yield product, which suggests that 5B is a key intermediate at or near the branch-point that leads either to product formation or to nonproductive "uncoupling" and H(2)O(2) production. The D251N mutation appears to perturb multiple stages in the catalytic cycle. (v) There is no spectroscopic evidence for the buildup of a high-valence oxyferryl/porphyrin pi-cation radical intermediate, 6. However, ENDOR spectroscopy of 7A in H(2)O and D(2)O buffers shows that 7A contains hydroxycamphor, rather than water, bound to Fe(3+), and that the proton removed from the C(5) carbon of substrate during hydroxylation is trapped as the hydroxyl proton. This demonstrates that hydroxylation of substrates by P450cam in fact occurs by the formation and reaction of 6. (vi) Annealing at > or = 220 K converts the initial product state 7A to the equilibrium product state 7, with the transition occurring via a second nonequilibrium product state, 7B, in the D251N mutant; in states 7B and 7 the hydroxycamphor hydroxyl proton no longer is trapped. (vii) The present results are discussed in the context of other efforts to detect intermediates in the P450 catalytic cycle.

Camphor↗
PubMed2004

Quantum mechanical/molecular mechanical investigation of the mechanism of C-H hydroxylation of camphor by cytochrome P450cam: theory supports a two-state rebound mechanism.

The stereospecific cytochrome P450-catalyzed hydroxylation of the C(5)-H((5-exo)) bond in camphor has been studied theoretically by a combined quantum mechanical/molecular mechanical (QM/MM) approach. Density functional theory is employed to treat the electronic structure of the active site (40-100 atoms), while the protein and solvent environment (ca. 24,000 atoms) is described by the CHARMM force field. The calculated energy profile of the hydrogen-abstraction oxygen-rebound mechanism indicates that the reaction takes place in two spin states (doublet and quartet), as has been suggested earlier on the basis of calculations on simpler models ("two-state reactivity"). While the reaction on the doublet potential energy surface is nonsynchronous, yet effectively concerted, the quartet pathway is truly stepwise, including formation of a distinct intermediate substrate radical and a hydroxo-iron complex. Comparative calculations in the gas phase demonstrate the effect of the protein environment on the geometry and relative stability of intermediates (in terms of spin states and redox electromers) through steric constraints and electronic polarization.

Camphor↗
PubMed2006

The effect of heme environment on the hydrogen abstraction reaction of camphor in P450cam catalysis: a QM/MM study.

The discrepancies between the published QM/MM studies (Schöneboom, J. C.; Cohen, S.; Lin, H.; Shaik, S.; Thiel, W. J. Am. Chem. Soc. 2004, 126, 4017; Guallar, V.; Friesner, R. A. J. Am. Chem. Soc. 2004, 126, 8501) on H-abstraction of camphor in P450cam have largely been resolved. The crystallographic water molecule 903 situated near the oxo atom of Compound I acts as a catalyst for H-abstraction, lowering the barrier by about 4 kcal/mol. Spin density at the A-propionate side chain of heme can occur in the case of incomplete screening but has no major effect on the computed barrier.

Camphor↗
PubMed2006

Mechanisms of reaction in cytochrome P450: Hydroxylation of camphor in P450cam.

The fundamental nature of reactivity in cytochrome P450 enzymes is currently controversial. Modelling of bacterial P450cam has suggested an important role for the haem propionates in the catalysis, though this finding has been questioned. Understanding the mechanisms of this enzyme family is important both in terms of basic biochemistry and potentially in the prediction of drug metabolism. We have modelled the hydroxylation of camphor by P450cam, using combined quantum mechanics/molecular mechanics (QM/MM) methods. A set of reaction pathways in the enzyme was determined. We were able to pinpoint the source of the discrepancies in the previous results. We show that when a correct ionization state is assigned to Asp297, no spin density appears on the haem propionates and the protein structure in this region remains preserved. These results indicate that the haem propionates are not involved in catalysis.

Aspartic Acid↗