LC/MS quantitative study of glucose by iodine attachment

We explored the potential of iodine attachment to improve the sensitivity of glucose measurement by LC/MS. After sample preparation, glucose was separated by normal phase chromatography, followed by anionization by I⁻-attachment prior to MS by post-column addition of a methanolic solution of iodoform. Iodine is capable of forming an anionic adduct with neutral monosaccharides in negative ion mode electrospray mass spectrometry. Quasi-molecular ions [M + I]⁻ of glucose, and [6,6-²H₂]glucose (abbreviated d₂-glucose) internal standard were quantitated in selected ion monitoring (SIM) mode. Iodine attachment LC/MS analysis provided high sensitivity, superior to GC/MS. It greatly simplified sample preparation and increased throughput. The advantages of iodine attachment can be realized even on old mass spectrometers. A LOD of 50 pg glucose on column was achieved. Due to iodine's predisposition to sublimate, the iodoform concentration must be minimized, which adds complexity to method development. To optimize reagent concentration we developed an efficient and flexible gradient-based delivery platform. Strategy for method development with iodoform is given.     

Determination of phosphorus by instrumental neutron activation and bremsstrahlung measurement in bone samples

The application of charge plate technique in studying the recoil reactions of¹²⁸I species originating from iodoform following neutron capture in pyridine medium is discussed emphasis being placed on the problem of reactions of energetic iodine species with the radiolytically generated quasi-free electrons. Ag/AgI electrodes, under a potential gradient of 83 V·cm^–1 are employed in collecting the nucleogenic iodine species from the irradiated iodoform-pyridine mixtures. It is observed that only¹²⁸I^– species are deposited on the anode plate showing a fairly high order of radioactivity. Collected activities are increased with increasing concentration of iodoform in the system, however, no¹²⁸I^– species are deposited on cathode surface and the activities are found nil upto the concentration range studied. It could be deduced that the recoil reactions taking place in pure iodoform are specifically influenced by the chemical reactivity of pyridine thereby govems the electrode deposition pattem in iodoform-pyridine molecular liquid mixtures.Part III:M. R. Zaman, S. P. Mishra, J. Chem. Soc. Pakistan, 16 (1994) 163.Work done in the Department of Chemistry, Banaras Hindu University, India, while holding a Fellowship of the Department of Human Resource Development, Govemment of India.     

Exchange of bromine and chlorine by iodine in aliphatic halides catalyzed by iron pentacarbonyl

Conclusions Iodine and iodoform in the presence of Fe(CO)₅ are effective reagents for the exchange of Br and Cl by iodine at the primary carbon atom of an aliphatic chain.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1 pp. 226–228, January, 1985.     

A topological investigation of the nonlinear optical compound: iodoform octasulfur

The crystal structure of the nonlinear optical material, iodoform octasulfur (CHI3.(S8)3), in the polar space group R3m, has been shown to contain three unique S...I and several S...S close contacts (相似文献   

Thermal properties of diene elastomers

The paper presents the results of investigating the effect of the macromolecule chemical structure and the spatial network structure of butadiene (BR), butadiene-styrene (SBR) and butadiene-acrylonitrile (NBR) rubbers on their thermal properties. The rubbers were cross-linked by the conventional method by means of dicumyl peroxide or sulfur as well as by the non-conventional way using iodoform (CH₃I). The rubber and their vulcanizates were assessed by the derivatographic method (under air) and by means of differential scanning calorimetry (DSC) under inert gas. The thermal cross-linking degree of the polydienes and the efficiency of the cross-linking processes, dependent on both the chemical structure of elastomer macromolecules and their spatial network structure were determined. The cross-linking of elastomers with iodoform changes the thermal properties of polymers, significantly increasing their glass transition temperature during both sample heating and cooling, which results from the increase in mutual interaction of macromolecules connected with their modification with iodine compounds.     

266 nm photolysis of CF3I and C2F5I studied by diode laser gain FM spectroscopy

Frequency modulated diode laser based absorption at 1.315 microm has been used to measure the Doppler lineshapes of the I((2)P(1/2)-(2)P(3/2)) transition in atomic iodine produced from the 266 nm photolysis of both CF(3)I and C(2)F(5)I. Wavelength resolved laser gain is seen following photolysis as excited iodine atoms ((2)P(1/2)) are produced with a quantum yield close to unity from photolysis of both parent molecules. Time resolved measurements were made and the nascent speed distribution and translational anisotropy parameter, beta were determined. Mean atomic speeds of 800 and 850 ms(-1), which correspond to 83 and 68% of the maximum possible kinetic energy release into the iodine photofragment, were determined for photolysis of CF(3)I and C(2)F(5)I, respectively. The nascent translational anisotropy parameter was found to be beta = 1.77 +/- 0.05 for CF(3)I and beta = 1.69 +/- 0.05 for C(2)F(5)I. These values are explicable in terms of parent rotational motion and non-adiabatic processes in the exit channel.     

PHOTOLYSIS OF IODODEOXYCYTIDINE IN DNA AND RELATED POLYNUCLEOTIDES: WAVELENGTH DEPENDENCE AND ENERGY TRANSFER*

Abstract— 5'-Iodocytosine (IC) containing denatured DNA and poly(C) were prepared and the photoinduced loss of iodine measured for irradiation at wavelengths between 240 and 313 nm. The following intrinsic quantum yields (Φ_INT) were obtained for irradiation at λ_ex > 300 nm where only IC absorbs: denatured DNA (0.01), poly(C) (0.013), apurinic acid (0.018) and IdCMP (0.026). These results suggest that geometrical or structural restraints in the polymer, which increase with the degree of base stacking, inhibit the loss of iodine from an excited IC residue. The variation in the photochemical cross section for iodine photolysis was measured as a function of the wavelength of irradiation and found to vary in a manner which indicates that absorption by noniodinated residues can lead to iodine photolysis. It is proposed that energy transfer from neighboring bases to an adjacent IC residue takes place, resulting in an action spectrum for iodine photolysis which reflects absorption of excitation energy by noniodinated as well as iodinated residues. The contribution due to energy transfer in denatured DNA was estimated to be from not more than a single base located on either side of an IC residue. The degree of transfer was slightly less in iodinated poly(C) and decreased 4-fold following depurination of the DNA. These results are consistent with a structurally dependent energy transfer process in which IC, because of its lower lying singlet state, can act as an energy trap.     

Fragmentation of alkoxy radicals: Mechanistic aspects of the tandemβ-fragmentation-intramolecular functionalization reaction

The formation of the β-peroxylactone (4) during the photolysis of lactol (3) with (diacetoxyiodo)-benzene (DIB) and iodine under oxygen atmosphere demostrates the presence of a peroxyradical intermediate in the tandem β-fragmentation-intramolecular functionalization reaction.     

Hypervalent organoiodine reagents in the β-fragmentation of bicyclic carbinolamides leading to imides

A mild and convenient method for the synthesis of 3,4-substituted cyclic imides by photolysis of bicyclic [3.3.0]- and [3.2.1]-carbinolamides in the presence of (diacetoxyiodo)-benzene and iodine is described.     

Photolytic cage effect of iodine in gases at high pressures

The photolysis of iodine has been studied in the gas phase using laser flash photolysis at 6943 A. The dependence of the quantum yield on the pressure has been investigated in the range 0.1–1000 atm for several inert gases. For Kr, Xe, O₂, CO₂, CH₄, C₂H₆ and C₃H₈ a decrease of the quantum yield with increasing pressure was obtained; for He, Ne, Ar and H₂ no effect could be observed. These results may correspond to a photolycitc cage effect of iodine in the gas phase analogous to that known from the liquid phase.     

The Photolysis of Iodoaromatic Compounds

Under appropriate conditions, the photolysis of iodoaromatic compounds yields derivatives of biphenyl and phenanthrene, as well as organometallic compounds. Ring closures of o-terphenyls to triphenylenes and of benzanilides to phenanthridones are described. The formation of dehydrobenzene (benzyne) on photolysis of 1,2-diiodobenzene in solution has been established. The photolysis of various substituted iodoaromatic compounds or of substances such as CH₃I, ICN, ICH₃, COOH, or RC?CI, provides a general method for the generation of a large variety of free radicals in solution. The potential uses of photochemically initiated exchanges of iodine in ArI for ¹³¹I, Li, D, Cl, or Br are noted.     

Diastereoselective Radical Hydroacylation of Alkylidenemalonates with Aliphatic Aldehydes Initiated by Photolysis of Hypervalent Iodine(III) Reagents

Diastereoselective radical hydroacylation of chiral alkylidenemalonates with aliphatic aldehydes is realized by the combination of a hypervalent iodine(III) reagent and UV‐light irradiation. The reaction is initiated by the photolysis of hypervalent iodine(III) reagents under mild, metal‐free conditions, and is the first example of diastereoselective addition of acyl radicals to olefins to afford chiral ketones in a highly stereoselective fashion. The obtained optically active ketones are useful chiral synthons, as exemplified by the short formal synthesis of (?)‐methyleneolactocin.     

Methyl Iodide Photodissociation at 193 nm: The I((2)P(1/2)) Quantum Yield

Methyl iodide photolysis at 193 nm has been studied through probing the I((2)P(1/2)-(2)P(3/2)) transition in the atomic iodine photofragment using diode laser spectroscopy. The I((2)P(1/2)) quantum yield has been determined through two different diode laser techniques and then compared. Frequency-modulated diode laser based absorption spectroscopy was used to extract nascent Doppler lineshapes from which an I((2)P(1/2)) quantum yield of unity is inferred. However when diode laser gain/absorption measurements were made, an I((2)P(1/2)) quantum yield of 0.68 ± 0.04 was found. The reason for this discrepancy is shown to lie in the diode laser gain/absorption method. Molecular iodine is found to be formed during the experiment via atomic iodine recombination and then in turn dissociates to produce both I((2)P(1/2)) and I((2)P(3/2)), thus distorting the returned quantum yield. This conclusion is supported both by the reduction of the I((2)P(1/2)) quantum yield with number of photolysis laser shots when measured using this technique and by the presence of fluoresence which is shown to have excited-state lifetimes and quenching rates that are consistent with those previously measured for the D and D' states of molecular iodine.     

The temperature dependence of the cage effect in the gas phase

The photodissociation of iodine has been studied in the gas phase by laser flash photolysis. The decrease of the quantum yield with increasing ethane and propane pressure has been interpreted in terms of the cage effect. As the temperature is increased a less pronounced cage effect is observed. The trends in the measured quantum yields with changing temperature and pressure agree with model calculations for dissociation in a viscous continuum. However the simple model applied is not useful for quantitative predictions. A small decrease of the second order rate constant for iodine atom recombination has been observed with increasing temperature.     

Ultraviolet photodissociation of iodine monochloride (ICl) at 235, 250, and 265 nm

ICl photolysis in the ultraviolet region of the spectrum (235-265 nm) is studied using the Slice Imaging technique. The Cl?((2)P(1/2))/Cl((2)P(3/2)) and the I?((2)P(1/2))/I((2)P(3/2)) branching ratio between the I((2)P(3/2)) + Cl((2)P(3/2))∕Cl?((2)P(1/2)) and I?((2)P(1/2)) + Cl((2)P(3∕/2))∕Cl?((2)P(1/2)) channels is extracted from the respective iodine and chlorine photofragment images. We find that ground state chlorine atoms (Cl((2)P(3/2))) are formed nearly exclusively with excited state iodine atoms (I?((2)P(1/2))), while excited spin-orbit chlorine atoms (Cl?((2)P(1/2))) are concurrently produced only with ground state iodine atoms (I((2)P(3/2))). We conclude that photolysis of ICl in this UV region is a relatively "clean" source of spin-orbit excited chlorine atoms that can be used in crossed molecular beam experiments.     

Improvement of Biological Effects of Root-Filling Materials for Primary Teeth by Incorporating Sodium Iodide

Therapeutic iodoform (CHI₃) is commonly used as a root-filling material for primary teeth; however, the side effects of iodoform-containing materials, including early root resorption, have been reported. To overcome this problem, a water-soluble iodide (NaI)-incorporated root-filling material was developed. Calcium hydroxide, silicone oil, and NaI were incorporated in different weight proportions (30:30:X), and the resulting material was denoted DX (D5~D30), indicating the NaI content. As a control, iodoform instead of NaI was incorporated at a ratio of 30:30:30, and the material was denoted I30. The physicochemical (flow, film thickness, radiopacity, viscosity, water absorption, solubility, and ion releases) and biological (cytotoxicity, TRAP, ARS, and analysis of osteoclastic markers) properties were determined. The amount of iodine, sodium, and calcium ion releases and the pH were higher in D30 than I30, and the highest level of unknown extracted molecules was detected in I30. In the cell viability test, all groups except 100% D30 showed no cytotoxicity. In the 50% nontoxic extract, D30 showed decreased osteoclast formation compared with I30. In summary, NaI-incorporated materials showed adequate physicochemical properties and low osteoclast formation compared to their iodoform-counterpart. Thus, NaI-incorporated materials may be used as a substitute for iodoform-counterparts in root-filling materials after further (pre)clinical investigation.     

Metal‐Free C?H Bond Activation of Branched Aldehydes with a Hypervalent Iodine(III) Catalyst under Visible‐Light Photolysis: Successful Trapping with Electron‐Deficient Olefins

Direct acyl radical formation of linear aldehydes (RCH₂‐CHO) and subsequent hydroacylation with electron‐deficient olefins can be effected with various types of metal and nonmetal catalysts/reagents. In marked contrast, however, no successful reports on the use of branched aldehydes have been made thus far because of their strong tendency of generating alkyl radicals through the facile decarbonylation of acyl radicals. Here, use of a hypervalent iodine(III) catalyst under visible light photolysis allows a mild way of generating acyl radicals from various branched aldehydes, thereby giving the corresponding hydroacylated products almost exclusively. Another characteristic feature of this approach is the catalytic use of hypervalent iodine(III) reagent, which is a rare example on the generation of radicals in hypervalent iodine chemistry.     

Metal‐Free CH Bond Activation of Branched Aldehydes with a Hypervalent Iodine(III) Catalyst under Visible‐Light Photolysis: Successful Trapping with Electron‐Deficient Olefins

Direct acyl radical formation of linear aldehydes (RCH₂‐CHO) and subsequent hydroacylation with electron‐deficient olefins can be effected with various types of metal and nonmetal catalysts/reagents. In marked contrast, however, no successful reports on the use of branched aldehydes have been made thus far because of their strong tendency of generating alkyl radicals through the facile decarbonylation of acyl radicals. Here, use of a hypervalent iodine(III) catalyst under visible light photolysis allows a mild way of generating acyl radicals from various branched aldehydes, thereby giving the corresponding hydroacylated products almost exclusively. Another characteristic feature of this approach is the catalytic use of hypervalent iodine(III) reagent, which is a rare example on the generation of radicals in hypervalent iodine chemistry.     

β-Fragmentation of alkoxy radicals. An approach to the synthesis of ring a of vernolepin

A model of ring A of vernolepin is synthesized by 1,4-fragmentation of γ-thiyl and γ-stannyl alkoxy-radicals, generated by photolysis of the corresponding δ-lactols (4) and (5) in the presence of iodosobenzene diacetate and iodine. It should be pointed out that the δ-lactone ring and the angular vinyl group are introduced in one step.     

FLASH PHOTOLYSIS OF 3-IODOTYROSINE IN AQUEOUS SOLUTION AT pH 5

Abstract— The 3-tyrosinyl free radicals (3-Tyr) and iodine atom are formed by flash photolysis of 3-iodotyrosine (3-Tyr-I) in aqueous solutions at pH 5. The presence of iodine atoms in the medium is characterized by the absorption spectrum and the decay kinetics of I formed when KI is added to the system. In the absence of radical scavengers, the 3-Tyr adds to or reacts with the parent molecule to produce a transient species, probably a radical dimer, which has an absorption maximum at 405 nm. The decay of this transient follows second order kinetics whose rate constant increases with decreasing 3-iodotyrosine concentration. Measurements of the dependence of the transient yield on the concentration of added ethanol indicate that the 3-Tyr radical reacts with ethanol by hydrogen abstraction. The rate constants of reaction of the 3-Tyr radical with 3-iodotyrosine and ethanol are deduced from results.