- Solvent and temperature probes of the long-range electron-transfer step in tyramine β-monooxygenase: Demonstration of a long-range proton-coupled electron-transfer mechanism
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Tyramine β-monooxygenase (TβM) belongs to a family of physiologically important dinuclear copper monooxygenases that function with a solvent-exposed active site. To accomplish each enzymatic turnover, an electron transfer (ET) must occur between two solvent-separated copper centers. In wild-type TβM, this event is too fast to be rate limiting. However, we have recently shown [Osborne, R. L.; et al. Biochemistry 2013, 52, 1179] that the Tyr216Ala variant of TβM leads to rate-limiting ET. In this study, we present a pH-rate profile study of Tyr216Ala, together with deuterium oxide solvent kinetic isotope effects (KIEs). A solvent KIE of 2 on kcat is found in a region where kcat is pH/pD independent. As a control, the variant Tyr216Trp, for which ET is not rate determining, displays a solvent KIE of unity. We conclude, therefore, that the observed solvent KIE arises from the rate-limiting ET step in the Tyr216Ala variant, and show how small solvent KIEs (ca. 2) can be fully accommodated from equilibrium effects within the Marcus equation. To gain insight into the role of the enzyme in the long-range ET step, a temperature dependence study was also pursued. The small enthalpic barrier of ET (Ea = 3.6 kcal/mol) implicates a significant entropic barrier, which is attributed to the requirement for extensive rearrangement of the inter-copper environment during PCET catalyzed by the Tyr216Ala variant. The data lead to the proposal of a distinct inter-domain pathway for PCET in the dinuclear copper monooxygenases.
- Zhu, Hui,Sommerhalter, Monika,Nguy, Andy K. L.,Klinman, Judith P.
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- Photoactivatable, biologically-relevant phenols with sensitivity toward 2-photon excitation
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Spatio-temporal release of biologically relevant small molecules provides exquisite control over the activation of receptors and signaling pathways. This can be accomplished via a photochemical reaction that releases the desired small molecule in response to irradiation with light. A series of biologically-relevant signaling molecules (serotonin, octopamine, capsaicin, N-vanillyl-nonanoylamide, estradiol, and tyrosine) that contain a phenol moiety were conjugated to the 8-bromo-7-hydroxyquinolinyl (BHQ) or 8-cyano-7-hydroxyquinolinyl (CyHQ) photoremovable protecting groups (PPGs). The CyHQ caged compounds proved sensitive toward 1PE and 2PE processes with quantum efficiencies of 0.2-0.4 upon irradiation at 365 nm and two-photon action cross sections of 0.15-0.31 GM when irradiated at 740 nm. All but one BHQ caged compound, BHQ-estradiol, were found to be sensitive to photolysis through 1PE and 2PE with quantum efficiencies of 0.30-0.40 and two photon cross sections of 0.40-0.60 GM. Instead of releasing estradiol, BHQ-estradiol underwent debromination.
- McLain, Duncan E.,Rea, Adam. C.,Widegren, Magnus B.,Dore, Timothy M.
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p. 2151 - 2158
(2015/12/04)
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- Novel amide- and sulfonamide-based aromatic ethanolamines: Effects of various substituents on the inhibition of acid and neutral ceramidases
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In the present study we describe the design and synthesis of a series of amide- and sulfonamide-based compounds as inhibitor of recombinant acid and neutral ceramidases. Inhibition of ceramidases has been shown to induce apoptosis and to increase the efficacy of conventional chemotherapy in several cancer models. B-13, lead in vitro inhibitor of acid ceramidase has been recently shown to be virtually inactive towards lysosomal acid ceramidase in living cells at lower concentrations and for a shorter time of treatment, suggesting the development of more potent inhibitors. In this study, a detailed SAR investigation has been performed to understand the effect of different substituents on the phenyl ring of amide- and sulfonamide-based compounds that partially resemble the structure of well-known inhibitors such as B-13, D-e-MAPP as well as NOE. Our results suggest that the electronic effects of the substituents on phenyl ring in B-13 and D-e-MAPP analogues have negligible effects either in enhancing the inhibition potencies or for selectivity towards aCDase over nCDase. However, the hydrophobicity and the steric effects of longer alkyl chains (n-Pr, n-Bu or t-Bu groups) at the phenyl ring were found to be important for an enhanced selectivity towards aCDase over nCDase.
- Bhabak, Krishna P.,Arenz, Christoph
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p. 6162 - 6170
(2012/11/06)
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- Iron-catalyzed aminohydroxylation of olefins
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We have discovered that N -sulfonyl oxaziridines react with a broad range of olefins in the presence of iron salts to afford 1,3-oxazolidines. This process provides access to 1,2-aminoalcohols with the opposite sense of regioselectivity produced from the copper-catalyzed oxyamination previously reported by our laboratories. Thus, either regioisomeric form of 1,2-aminoalcohols can easily be obtained from the reaction of oxaziridines with olefins, and the sense of regioselectivity can be controlled by the appropriate choice of inexpensive, nontoxic, first-row transition-metal catalyst.
- Williamson, Kevin S.,Yoon, Tehshik P.
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supporting information; experimental part
p. 4570 - 4571
(2010/06/12)
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- Enantiomers of adrenaline-type amino alcohols by Burkholderia cepacia lipase-catalyzed asymmetric acylation
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The enantiomers of norphenylephrine and octopamine were prepared using lipase PS-catalyzed enantioselective acylation with butanoic anhydride. Burkholderia cepacia lipase-catalyzed acylation with butanoic anhydride was used for the preparation of pharmaceutically important norphenylephrine and octopamine enantiomers, all in 98% ee. Reactivity of the phenolic OH groups and easy racemization, especially in the case of octopamine, complicated optimization. For norphenylephrine, chemical N-acylation was fast and allowed the subsequent enzymatic benzylic acylation in situ. The preparation of the octopamine enantiomers became possible by using the N-Fmoc protected substrate and by the Candida antarctica lipase B-catalyzed deprotection of the OH groups before the N-deprotection was performed.
- Lundell, Katri,Katainen, Erja,Kiviniemi, Anu,Kanerva, Liisa T.
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p. 3723 - 3729
(2007/10/03)
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- Compositions containing carbohydrates obtained from plants of the family cactacea
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Therapeutic formulations for the treatment of inflammation, pain, pruritis and local hyperthermia are based on carbohydrate/amine compositions obtained from plants of the family Cactaceae.
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- Pharmaceutical formula
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The present invention concerns a pharmacological vehicle or carrier system, which makes possible administration of the active ingredient with a high absorption thereof in the blood circulation of the patient treated therewith, in particular also in the case of oral administration. The pharmacological vehicle system according to the invention comprises ultrafine particles of a reaction product of a reactive derivative of an at least dibasic inorganic acid or an alkane-carboxylic acid having 2 or 3 carboxyl groups and optionally one or two hydroxy groups, wherein one bond of the dibasic inorganic acid or one carboxy group of the alkane-carboxylic acid is bonded to a pharmacological active ingredient containing a hydroxy group, SH group and/or a primary or secondary amino group having a ractive hydrogen atom on this group, and the other bond is bonded to the free hydroxy group of a glycerolipid having at least one free hydroxy group on the glycerol. The invention further concerns these reaction products and a process for the preparation of ultrafine particles of these reaction products.
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- A NEW ENTRY TO THE SYNTHESIS OF β-HYDROXYTYROSINES VIA A NOVEL BENZYLIC HYDROXYLATION
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Highly stereoselective introduction of a hydroxyl group into the benzylic position of N-tert-butoxycarbonyl-L-tyrosine derivatives was achieved by the use of K2S2O8/CuSO4 system to give the threo cyclic carbamates.These were converted into β-hydroxytyrosine and octopamine, efficiently.
- Shimamoto, Keiko,Ohfune, Yasufumi
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p. 5177 - 5180
(2007/10/02)
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