Elemental analysis of Korean women’s blood serums using instrumental neutron activation analysis

Instrumental neutron activation analysis was used to assess the concentration of the inorganic trace elements in Korean women’s blood serums. It was found that a high concentration of Na and Cl incurs an analytical interference, but the 12 elements such as Br, Ca, Cl, Co, Cr, Cs, Fe, K, Na, Rb, Se and Zn could be determined under the condition of an interference minimization. Serum samples collected from 63 women were analyzed and the concentration level and range of the elements were evaluated. NIST SRMs were analyzed simultaneously for quality control. The average values of the Na and Cl determined in the serum samples were 3,365 and 3,533 mg/l, Ca was 96.4 mg/l and K was 191 mg/l. Besides, Br, Se and Zn have a concentration level of 6.46, 0.13 and 0.98 mg/l, respectively. It was found that there is no significant difference between the present values and the reported values.     

Characterisation of poly(neutral red) modified carbon film electrodes; application as a redox mediator for biosensors

The polymer redox mediator, poly(neutral red) (PNR), has been synthesised and characterised electrochemically to investigate the best electropolymerisation and mediation conditions for application in enzyme biosensors and to clarify the mechanism of action. Neutral red was electropolymerised by potential cycling on carbon film electrode substrates by allowing the monomer to be oxidised during the full 20 cycles of polymerisation or reducing the positive limit of the potential window after the first 2 cycles to impede monomer oxidation with a view to obtaining longer polymer chains and a lesser degree of branching. Comparison was made with glassy carbon substrates. The PNR films on carbon film electrodes were characterised using cyclic voltammetry and electrochemical impedance spectroscopy, as well as in glucose biosensors prepared with PNR. Glucose oxidase enzyme was immobilised by encapsulation in silica sol-gel and compared with that obtained by cross-linking with glutaraldehyde. The biosensors were evaluated by chronoamperometry in 0.1 M phosphate buffer saline solution, pH 7.0, and showed evidence of electron transfer between the enzyme cofactor flavin adenine dinucleotide and PNR dissolved in the enzyme layer competing with PNR-mediated electrochemical degradation of H₂O₂ formed during the enzymatic process. This paper is dedicated to Professor Dr. Algirdas Vaskelis on the occasion of his 70th birthday.     

In vivo microdialysis determination of collagen-induced serotonin release in rat blood

We developed a sensitive microbore HPLC method coupled with an on-line microdialysis system to simultaneously measure endogenous 5-hydroxytryptamine (serotonin; 5-HT) and its major metabolite 5-hydroxyindoleacetic acid (5-HIAA) in the rat blood in vivo. A dialysis tube was placed in the right jugular vein. The validity of the procedure is demonstrated because analysis of the aggregating agents, collagen (I mg/kg) plus epinephrine (0.3 mg/kg) after intravenous injection, showed that they induced an increase in 5-HT and 5-HIAA levels in the jugular vein of the rat.     

Synthesis of 3,5,7-Trioxapentacyclo[7.2.1.02,8.04,11.06,10]dodecane. A Novel Diacetal Trioxa-Cage

3,5,7-Trioxapentacyclo[7.2.1.0^2,8.0^4,11.0^6,10]dodecane, the parent compound of novel diacetal trioxa-cages, was synthesized from maleic anhydride cyclopentadiene adduct 1 by a four-step sequence. Attempts for the synthesis of monoaza dioxa-cage 12 failed. Ozonolysis of compound 9 in CH₂Cl₂-EtOH(1:1) at ?78°C followed by reduction with Me₂S gave 13 in 65% yield.     

Technological quality determination of pharmaceutical disintegrant by DSC cooling and DSC photovisual

A number of disintegrants are available on the market. They improve tablets’ disintegration. The objective of this work is the comparison of the technological quality parameters of disintegrants using different analytical techniques. Three batches of disintegrants and their binary mixtures (water:disintegrants) were investigated. Cooling experiments were used from –30 up to 200°C. The data obtained showed calorimetric differences between the samples. In the binary mixtures water showed different crystallization behaviour from the one found in the literature. According to the results DSC technique helped the quality control of different disintegrants.     

Thermodynamic characterization of different actin isoforms

Summary The thermodynamic properties of the cardiac and skeletal a-actin isoforms were studied to characterize the molecular bases of the functional differences between them with the method of differential scanning calorimetry (DSC). The thermal properties of the actin filaments were described in the presence of calcium and magnesium ions as well. Based on the calculated free energy changes the α-cardiac actin filaments appeared to be more stable in its physiologically more relevant, magnesium saturated form. The magnesium saturated form of the α-cardiac actin filaments seemed to be more stable compared to the calcium saturated form of it. The enthalpy and entropy changes could differentiate between the α-cardiac and α-skeletal actin isoforms and between the calcium and magnesium saturated cardiac actin isoforms as well. Our results can demonstrate that the few differences between the amino acid sequences of the α-actin isoforms have an influence on the thermal properties and maybe on the function of these proteins as well.     

1, n-Triorganosilyl migrations in the rearrangements of silyl-substituted organolithium compounds

Under the agency of the potent lithiating agent, n-butyllithium in TMEDA, an array of organosilanes was found to undergo 1, n-silyl rearrangements via carbanionic intermediates. Unambiguous 1, 2-, 1, 3- and 1, 4-silyl shifts were uncovered in 1-trimethylsilyl-1, 1, 2-triphenylethane, 1, 1-bis(trimethylsilyl)-1-phenylalkanes and 1, 2-bis(trimethylsilyl)-1, 2-diphenylethane, respectively. Cross-over and competition experiments established that these rearrangements generally are intramolecular and occur with decreasing ease in the order, 1, 2 > 1, 3 > 1, 4. In other compounds, such as 1, 1-bis(trimethylsilyl)-1, 2-diphenylethane, 1, n-bis(trimethylsilyl)benzenes and triphenyl(trimethylsilyl)methane, competing 1, n-silyl shifts occurred. Attack of the organolithium intermediates on solvent and silicon—lithium exchange were significant side reactions in some instances. 1-Trimethylgermyl-1, 1, 2-triphenylgermane underwent no discernible rearrangement but rather gave the product expected from germanium—lithium exchange. By conducting time and competition studies, it was shown that lithiation is the product-determining step in these rearrangements and that dual pathways, namely 1, 3-versus consecutive 1, 2- 1, 4-pathways, are operative in certain rearrangements.     

Polyarylates. III. Kinetic studies of interfacial polycondensation

The kinetics of interfacial polycondensation of bisphenol A with isophthaloyl chloride and terephthaloyl chloride in dichloromethane with triethylbenzylammonium chloride (TEBAC) as the catalyst was investigated via measurements of bisphenolate concentration by UV. The reaction was found to be second order with respect to bisphenolate. The dependence of the rate constant on stirring speed, amount of TEBAC, and reaction temperature was studied. The rate constant was increased with an increase of stirring speed, quantity of TEBAC added, as well as the reaction temperature. The activation energy was found to be 7.7 kcal/mol at a stirring speed of 700 rpm in the presence of 0.160 of TEBAC. The role of TEBAC was found to be interesting. It did not alter the equilibrium (the partition coefficient remained the same in the presence of TEBAC), but it did enhance the transfer rate of bisphenolate.     

The roles of the rel+ gene and of 4-thiouridine in killing and photoprotection of Escherichia coli by near-ultraviolet radiation

Abstract— Photoprotection is a reduction in response to far-UV (190–300. nm) radiation in cells that have been previously exposed to longer wavelengths. It has been proposed that photoprotection operates by means of a growth delay that permits more time for dark repair. Growth delay in Escherichia coli utilizes 4-thiouridine (⁴Srd) in transfer RNA as a chromophore and it requires the rel⁺ gene, which exerts a stringent control upon RNA synthesis. Mutants that were either rel or ⁴Srd^? were isolated from E. coli B, utilizing a near-UV-induced growth-delay selection technique. The rel mutants, which undergo little growth delay after near-UV irradiation, show only 50% as much photoprotection as wild types, while ⁴Srd^? mutants show no photoprotection at all. Thus, photoprotection appears to utilize ⁴Srd as its sole chromophore in E. coli B and B/r, and no more than 50% of photoprotection in these strains can be a result of near-UV-induced growth delay.     

Molecular basis for antifreeze activity difference of two insect antifreeze protein isoforms

The insect spruce budworm(Choristoneura fumiferana) produces antifreeze protein(AFP) to assist in the protection of the over-wintering larval stage and contains multiple isoforms. Structures for two isoforms,known as CfAFP-501 and CfAFP-337,show that both possess similar left-handed β-helical structure,although thermal hysteresis activity of the longer isoform CfAFP-501 is three times that of CfAFP-337. The markedly enhanced activity of CfAFP-501 is not proportional to,and cannot be simply accounted for,by the increased ice-binding site resulting from the two extra coils in CfAFP-501. In or-der to investigate the molecular basis for the activity difference and gain better understanding of AFPs in general,we have employed several different computational methods to systematically study the structural properties and ice interactions of the AFPs and their deletion models. In the context of intact AFPs,a majority of the coils in CfAFP-501 has better ice interaction and causes stronger ice lattice disruption than CfAFP-337,strongly suggesting a cooperative or synergistic effect among β-helical coils. The synergistic effect would play a critical role and make significant contributions to the anti-freeze activity β-helical antifreeze proteins. This is the first time that synergistic effect and its implica-tion for antifreeze activity are reported for β-helical antifreeze proteins.