Biomedical subjects
Publications and source records attributed to E Bagan.
We present the optimal scheme for estimating a pure qubit state by means of local measurements on N identical copies. We give explicit examples for low N. For large N, we show that the fidelity saturates the collective measurement bound up to order 1/N. When the signal state lays on a meridian of the Bloch sphere, we show that this can be achieved without classical communication.
We analyze the problem of sending, in a single transmission, the information required to specify an orthogonal trihedron or reference frame through a quantum channel made out of N elementary spins. We analytically obtain the optimal strategy, i.e., the best encoding state and the best measurement. For large N, we show that the average error goes to zero linearly in 1/N. Finally, we discuss the construction of finite optimal measurements.
Quantum states can be used to encode the information contained in a direction, i.e., in a unit vector. We present the best encoding procedure when the quantum state is made up of N spins (qubits). We find that the quality of this optimal procedure, which we quantify in terms of the fidelity, depends solely on the dimension of the encoding space. We also investigate the use of spatial rotations on a quantum state, which provide a natural and less demanding encoding. In this case we prove that the fidelity is directly related to the largest zeros of the Legendre and Jacobi polynomials. We also discuss our results in terms of the information gain.
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Two approaches have been used to develop nonmutagenic 5-nitroimidazoles. Both approaches are based on knowledge of the likely mechanisms by which this class of compounds cause mutagenicity. The first approach involved incorporating readily oxidizable gallate derivatives into the molecule. In one case, a very weakly mutagenic active antitrichomonal agent was obtained. The second approach involved incorporating a substituent at the C4 position of the ring. This generally resulted in a large reduction in mutagenicity and a lowering of antitrichomonal activity in vitro. In certain cases, however, mutagenicity was dramatically reduced while moderate antitrichomonal activity was retained. For example, 1,2-dimethyl-4-(2-hydroxyethyl)-5-nitroimidazole (5) showed good antitrichomonal activity in vitro (ED50 = 2 micrograms/kg) while possessing only 4% of the mutagenicity of metronidazole.
Substantial evidence implicates the obligatory nucleophilic attack by water at C4 for the elimination of the carbamate and subsequent immobilization by electrophilic attack on protein thiols. Consequently, the strong correlation between the structural requirements for protein alkylation and for mutagenicity in TA100 suggests a possible role of nucleophilic addition at C4 or at the 2-methylene carbon for the expression of mutagenicity. Further studies directed at evaluating this possibility are currently in progress.
An improved method for the preparation of bile acid methyl esters is described. This is achieved by the addition of catalytic amounts of p-toluenesulfonic acid in a solution of bile acid in methanol. Advantages of this procedure over conventional methods include (1) use of a mild solid acid catalyst which prevents the formation of undesirable byproducts, (2) isolation of a solid product of high purity and (3) utilization of a relatively safe reagent in comparison to other methods involving diazomethane, hydrochloric acid or sulfuric acid.
A convenient procedure for the synthesis of 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25-tetrol via a modified homologation sequence of the intermediate 3 alpha,7 alpha,12 alpha-triformyloxy-24-oxo-25-diazo-25-homo-5 beta-cholane involving a homogeneous medium is described. This involves treating the intermediate alpha-diazoketone in methanol with a solution of silver benzoate in triethylamine. Grignard reaction of the resulting triformyloxy methyl homocholate yielded 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25-tetrol. Large amounts of this bile alcohol were needed to further investigate the defect of cholic acid biosynthesis in patients with cerebrotendinous xanthomatosis (CTX).
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[3beta-3H]-bile acids and bile alcohols may be useful for metabolic studies in man and animals because the 3-position is invulnerable to bacterial attack. A number of tritium labeled bile acids and bile alcohols were prepared by selective oxidation of the hydroxyl group at carbon-3 followed by reduction with NaBT4. In each case, the bile acids and bile alcohols epimeric at carbon-3 were resolved by analytical and preparative thin-layer chromatography and characterized by gasliquid chromatography. The average yield was 60--65% and specific activities of the final products were in the range of 7.4 x 10(7) dpm/mg.