The effect of chain length on the melting temperature and size of dialkyldimethylammonium bromide vesicles

Differential scanning calorimetry (DSC) and dynamic light scattering (DLS) were used to obtain the gel to liquid-crystalline phase transition temperature (Tm) and the apparent hydrodynamic radius (Rh) of spontaneously formed cationic vesicles of dialkyldimethylammonium bromide salts (CnH2n+1)2(CH3)2N+.Br-, with varying chain lengths. The preparation of cationic vesicles from aqueous solution of these surfactants, for n=12, 14, 16 and 18 (DDAB, DTDAB, DHDAB and DODAB, respectively), requires the knowledge of the surfactant gel to liquid-crystalline phase transition temperature, or melting temperature (Tm) since below this temperature these surfactants are poorly or not soluble in water. That series of cationic surfactants has been widely investigated as vesicle-forming surfactants, although C12 and C18, DDAB and DODAB are by far the most investigated from this series. The dependence of Tm of these surfactants on the number n of carbons in the surfactant tails is reported. The Tm obtained by DSC increases non-linearly with n, and the vesicle apparent radius Rh is about the same for DHDAB and DODAB, but much smaller for DDAB.     

Micellar effects upon the reaction of cobalt complexes with alkyl halides.

The reactions of the cobalozime Co (DH)-2 and the related Co(DOH)DOpn0 are strongly catalyzed by cationic micelles of cetyltrimethylammonium bromide (CTABr). The rate enhancements for the cobaloxime reaction and for that of Co (DOH)DOpn0 (in parentheses) are: EtBr approximately 1 (8.5); n-C5H11Cl, 220 (200); ClCH2CO-2, 420 (173); ClCH2CH2CO-2, 373. Anionic micelles of sodium lauryl sulfate inhibit the reaction of Co(DOH)DOpn0 with ClCH2CO-2, but do not affect that with n-C5H11Cl. The reactions of Co(DOH)DOpn0, like those of the cobaloxime are SN2 displacements and in the absence of surfactant in MeOH n-PrBr is more reactive than iso-PrBr.     

Anion binding properties of human serum albumin from halide ion quadrupole relaxation.

The nuclear magnetic quadrupole relaxation enhancement of 35Cl-, 81Br-, and 12I- anions on binding to human serum albumin has been studied under conditions of variable protein and anion concentration and also in the presence of simple inorganic, amphiphilic, and complex anions which compete with the halide ions for the protein anion binding sites. Two classes of anion binding sites with greatly different binding constans were identified. Experiments at variable halide ion concentration were employed to determin the Cl- and I- binding constants. By means of 35 Cl nuclear magnetic resonance (NMR) the relative affinity for different anions was determined by competition experiments for both the strong and the weak anion binding sites. Anion binding follows the sequence SO42- smaller than F- smaller than CH3COO- smaller than Ci- smaller Br- smaller than NO3- smaller than I- smaller than ClO4- smaller than SCN- smaller than Pt(CN)42- smaller than Au(CN)2- smaller than CH3(CH2)11OSO3- for the high affinity sites, and the sequence SO42- congruent to F- congruent to Cl- smaller CH3COO- smaller than NO3- smaller than Br- smaller than I- smaller than ClO4- smaller than SCN- for the low affinity sites. These series are nearly identical with the well-known lyotropic series. Consequently, those effects of anions on proteins described by the lyotropic series can be correlated with the affinities of the anions for binding to the protein. The data suggest that the physical nature of the interaction is the same for both types of biding sites, and that the differences in affinity between different binding sites must be explained in terms of tertiary structure. Analogous experiments performed using 127I- quadrupole relaxation gave results very similar to those obtained with 35Cl-. A comparison between the Cl-, Br- and I- ions revealed that, as a result of the increasing affinity for the weak anion binding sites in the series Cl- smaller than Br- smaller than I-, Cl- is much more useful as a probe for the specific anion binding sites than the other two halide ions. The findings with human serum albumin in this and other respects are probably of general relevance in studies of protein-anion interactions. In addition to competition experiments, the magnitude of the relaxation rate is also discussed. Line broadening not related to anion binding to the protein is found to be small. A comparison of transverse and longitudinal 35Cl relaxation rates gives a value for the quadrupole coupling constant of the high affinity sites in good agreement with a calculated coupling constant assuming anion binding to arginine.     

Preparation and photophysical properties of a caged kynurenine

We have prepared l-kyurenine 4-hydroxyphenacyl ester, a caged derivative of L-kynurenine. N(α)-tBOC-L-tryptophan was reacted with 4-hydroxyphenacyl bromide in DMF with K(2)CO(3) as the base to give the N(α)-tBOC 4-hydroxyphenacyl ester. The ester was then treated with O(3) in MeOH at -20°C, followed by trifluoroacetic acid in CH(2)Cl(2), then aqueous HCl to obtain the caged kynurenine as the dihydrochloride salt. The caged kynurenine is stable as a dry solid in the dark at -78°C, but in aqueous solutions in phosphate buffer at pH 7-8 hydrolyzes rapidly (t(1/2) ～5 min). Solutions in Tris at pH 7 are more stable (t(1/2) >30 min), and solutions in 1mM HCl are stable for several hours. As expected, the ester is cleaved in microseconds with laser pulses at 355 nm. The caged kynurenine may be useful for preparation of substrate complexes for crystallography or in biological studies on kynurenine.     

Synthetic procedures to monomethyl-platinum(II) complexes containing nitrogen ligands of biological relevance

The complex trans-bis(dimethylsulfoxide)chloromethylplatinum(II) (1) is fairly soluble in water, where it undergoes multiple equilibria involving the formation of geometrically distinct [Pt(H(2)O)(DMSO)Cl(CH(3))] aqua-species. On reacting an aqueous solution of 1 with monodentate nitrogen donor ligands L, such as pyridines or amines, two well distinct patterns of behavior can be recognized: (i) a single stage fast substitution of one DMSO by the entering ligand, yielding a complex of the type trans(C,N)-[Pt(DMSO)(L)Cl(CH(3))] which contains four different groups coordinated to the metal and which undergoes a slow conversion into its cis-isomer, (ii) a double substitution affording cationic complex ions of the type cis-[Pt(L)(2)(DMSO)(CH(3))](+). When this latter reaction is carried out using sterically hindered ligands, slow rotation of the bulk ligand around the Pt[bond]N bond allows for the identification of head-to-head and head-to-tail rotamers in solution, through (1)H NMR spectrometry. The addition of chloride anion to 1 leads to the anionic species cis-[Pt(DMSO)Cl(2)(CH(3))](-), where a molecule of DMSO still remains coordinated to the metal center, despite its quite fast rate of ligand exchange (k(exch) with free DMSO=12+/-1 s(-1)). The reaction of complex 1 with bidentate ligands, such as ethylenediamine (en) or simple amino acids, leads to the cationic species [Pt(en)(DMSO)(CH(3))](+) or to the neutral [Pt(DMSO)(N[bond]O)(CH(3))], (where N[bond]-O[double bond]GlyO(-), AlaO(-)).     

Sequence specificity modification of double-stranded DNA with an alkylating derivative of oligodeoxyribonucleotide pT(CT)6

It is shown that in slightly acidic solution (pH approximately 5.3) reagent CIRCH2NHpT(CT)6 (RCl = -C6H4-N(CH3)CH2CH2Cl) modifies a double-stranded DNA fragment (120 b. p.) containing A(GA)6.T(CT)6 sequence at a single nucleotide residue, viz. G29 located near to this sequence in the DNA chain. The location of this modification point suggests formation of a triple-stranded reactive complex with parallel orientation of the pyrimidine oligonucleotide moiety of the reagent and pyrine sequence of the target DNA. Analysing the modification extent dependence of the reagent concentration the association constant Kx between the reagent and DNA was calculated (Kx = (0.95 +/- 0.03).10(5) M-1, 25 degrees C, pH = 5.3, [NaCl] = 0.1 M). The modification by the reagent ClRCH2NHpT(m5CT)6 has the same quantitative characteristics as in the case of ClRCH2NHpT(CT)6.     

Synthesis, characterization, and mesophase formation of phenylacetoxy cellulose and its halogenated derivatives

A series of phenylacetoxy cellulosics with degrees of substitution (DS) between 1.4 and 3.0 and different halogenation (2-chloro, 3-chloro, 4-chloro, 2,4-dichloro, 3,4-dichloro, and 4-bromo) were synthesized. All the prepared phenylacetoxy cellulosics were soluble in dimethylformamide (DMF) and DMAc. The solubility increased with increasing DS. Mesophases were observed for all of the phenylacetoxy cellulosics with low to medium DS (DS < 2.5) in DMF and DMAc. Non- or mono-halogeneated phenylacetoxy cellulosics with high DS (DS > 1.9) were soluble in methylene chloride (CH2Cl2), whereas those with very low DS or di-halogenation on the phenyl ring were only slightly swollen or partially soluble in CH2Cl2. Non- and mono-halogenated phenylacetoxy cellulosics were soluble in DMSO and formed liquid crystals regardless of the DS, in contrast to CH2Cl2 solutions which display liquid crystalline behavior at medium to high DS (DS > 1.9) only. The solubility of the di-halogenated phenylacetoxy cellulosics in DMSO was limited to approximately 40 wt %.     

X-ray structure of the curare alkaloid (+)-tubocurarine dibromide.

X-ray structure determination of the compound (C37H42N2O6)2+ .2Br-.4CH3OH, confirms that (+)-tubocurarine is a monoquaternary salt and has established that the molecule adopts different conformations in crystals of the dibromide and dichloride salts. The crystal structure is stabilised by a number of hydrogen bonds involving the two free hydroxyl groups and the tertiary nitrogen of the tubocurarine molecule, the bromide ions and the solvent molecules. The absolute configuration of the molecule, determined by X-ray anomalous scattering, confirms the configuration assigned earlier by chemical studies.     

Catalytic mechanism of dichloromethane dehalogenase from Methylophilus sp. strain DM11

The glutathione (GSH)-dependent dichloromethane dehalogenase from Methylophilus sp. strain DM11 catalyzes the dechlorination of CH(2)Cl(2) to formaldehyde via a highly reactive, genotoxic intermediate, S-(chloromethyl)glutathione (GS-CH(2)Cl). The catalytic mechanism of the enzyme toward a series of dihalomethane and monohaloethane substrates suggests that the initial addition of GSH to the alkylhalides is fast and that the rate-limiting step in turnover is the release of either the peptide product or formaldehyde. With the exception of CH(2)ClF, which forms a relatively stable GS-CH(2)F intermediate, the turnover numbers for a series of dihalomethanes fall in a very narrow range (1-3 s(-1)). The pre-steady-state kinetics of the DM11-catalyzed addition of GSH to CH(3)CH(2)Br exhibits a burst of S-(ethyl)-glutathione (k(b) = 96 +/- 56 s(-1)) followed by a steady state with k(cat) = 0.13 +/- 0.01 s(-1). The turnover numbers for CH(3)CH(2)Cl, CH(3)CH(2)Br, and CH(3)CH(2)I are identical, indicating a common rate-limiting step. The turnover numbers of the enzyme with CH(3)CH(2)Br and CH(3)CH(2)I are dependent on viscosity and are very close to the measured off-rate of GSEt. The turnover number with CH(2)I(2) is also dependent on viscosity, suggesting that a diffusive step is rate-limiting with dihaloalkanes as well. The rate constants for solvolysis of CH(3)SCH(2)Cl, a model for GS-CH(2)Cl, range between 1 s(-1) (1:1 dioxane/water) and 64 s(-1) (1:10 dioxane/water). Solvolysis of the S-(halomethyl)glutathione intermediates may also occur in the active site of the enzyme preventing the release of the genotoxic species. Together, the results indicate that dissociation of the GS-CH(2)X or GS-CH(2)OH intermediates from the enzyme may be a relatively rare event.     

Acylation of carbohydrates over Al2O3: preparation of partially and fully acylated carbohydrate derivatives and acetylated glycosyl chlorides

Selective and per-O-acylation of carbohydrate derivatives using acyl chlorides and Al2O3, a solid support reagent, is reported. This protocol does not require the addition of any base or activator. This methodology has been further extended to the selective acylation of carbohydrate diols and the one-pot preparation of acetylated glycosyl chlorides direct from free reducing sugars. The yields obtained in most of the cases are excellent.     

'O-Acyl isopeptide method' for peptide synthesis: Solvent effects in the synthesis of Abeta1-42 isopeptide using 'O-acyl isodipeptide unit'.

'O-Acyl isopeptide method' is an efficient synthetic method for peptides. We designed 'O-acyl isodipeptide units', Boc-Ser/Thr(Fmoc-Xaa)-OH, as important building blocks to enable routine use of the O-acyl isopeptide method. In the synthesis of an Abeta1-42 isopeptide using O-acyl isodipeptide unit Boc-Ser(Fmoc-Gly)-OH, a side reaction, resulting in the deletion of Ser(26) in the O-acyl isopeptide structure, was noticed during coupling of the unit. We observed that the side reaction occurred during the activation step and was solvent-dependent. In DMF or NMP, an intramolecular side reaction, originating from the activated species of the unit, occurred during the activation step. In non-polar solvents such as CHCl(3) or CH(2)Cl(2), the side reaction was less likely to occur. Using CH(2)Cl(2) as solvent in coupling the unit, the target Abeta1-42 isopeptide was synthesized with almost no major side reaction.     

Acyl migration on nucleic acid compounds related to adenosine

Treatment of N6,N6-di-p-toluyl-2',3'-O-isopropylideneadenosine (7) with ZnBr2 in 1,4-dioxane afforded a 8,5'-O-cycloadenosine derivative 8 exclusively. Reaction of 2',3'-O-isopropylideneadenosine (1) with p-cyanobenzoyl chloride in a CH2Cl2-Et3N mixture afforded a ring-cleaved compound 11 as the main product.     

Purification of acetylcholinesterase from horse erythrocytes using affinity chromatography

A commercial preparation of water-soluble acetylcholinesterase from horse red cells has been purified to a specific activity of 2380 U/mg of protein (a 1660-fold purification) by a twofold affinity chromatography on the known sorbent of Sepharose-p-[NH-(CH2)5-C(O)NH(CH2)5C(O)NH-]-C6H4-N+(CH3)3 X Br- at pH 7.5. A selective elution of the enzyme was carried out from 10 mM of the phosphate buffer solution which contains 0.2% of triton X-100. Subsequent desorption of the enzyme proceeded with 5 mM of phenyltrimethylammonium bromide introduced into the buffer. Such effective preparations of acetylcholinesterase have not been previously produced. Effectiveness of the affinity sorbents considerably depends on the nature of the ligand which is covalent-linked with a Sepharose matrix and on the length of the attachment spacer arm ("insert") between them. A reversible inhibitory effect of certain ligands (tetramethylammonium, phenyltrimethylammonium) and their derivatives on acetylcholinesterase is estimated in comparison.     

A facile stereoselective synthesis of alpha-glycosyl ureas

Alpha-glycosyl ureas can be synthesised directly from tetra-O-benzyl glycosyl azides and isocyanates, using a one-pot procedure that is simple and general in scope. The benzyl protecting groups are easily removed from the urea products by catalytic hydrogenation. The synthesised alpha-glycosyl ureas represent a new class of neo-glycoconjugates with the potential of being resistant towards carbohydrate processing enzymes.     

Comparison of the Efficacies of Chloromethane, Methionine, and S-Adenosylmethionine as Methyl Precursors in the Biosynthesis of Veratryl Alcohol and Related Compounds in Phanerochaete chrysosporium

The effect on veratryl alcohol production of supplementing cultures of the lignin-degrading fungus Phanerochaete chrysosporium with different methyl-(sup2)H(inf3)-labelled methyl precursors has been investigated. Both chloromethane (CH(inf3)Cl) and l-methionine caused earlier initiation of veratryl alcohol biosynthesis, but S-adenosyl-l-methionine (SAM) retarded the formation of the compound. A high level of C(sup2)H(inf3) incorporation into both the 3- and 4-O-methyl groups of veratryl alcohol occurred when either l-[methyl-(sup2)H(inf3)]methionine or C(sup2)H(inf3)Cl was present, but no significant labelling was detected when S-adenosyl-l-[methyl-(sup2)H(inf3)]methionine was added. Incorporation of C(sup2)H(inf3) from C(sup2)H(inf3)Cl was strongly antagonized by the presence of unlabelled l-methionine; conversely, incorporation of C(sup2)H(inf3) from l-[methyl-(sup2)H(inf3)]methionine was reduced by CH(inf3)Cl. These results suggest that l-methionine is converted either directly or via an intermediate to CH(inf3)Cl, which is utilized as a methyl donor in veratryl alcohol biosynthesis. SAM is not an intermediate in the conversion of l-methionine to CH(inf3)Cl. In an attempt to identify the substrates for O methylation in the metabolic transformation of benzoic acid to veratryl alcohol, the relative activities of the SAM- and CH(inf3)Cl-dependent methylating systems on several possible intermediates were compared in whole mycelia by using isotopic techniques. 4-Hydroxybenzoic acid was a much better substrate for the CH(inf3)Cl-dependent methylation system than for the SAM-dependent system. The CH(inf3)Cl-dependent system also had significantly increased activities toward both isovanillic acid and vanillyl alcohol compared with the SAM-dependent system. On the basis of these results, it is proposed that the conversion of benzoic acid to veratryl alcohol involves para hydroxylation, methylation of 4-hydroxybenzoic acid, meta hydroxylation of 4-methoxybenzoic acid to form isovanillic acid, and methylation of isovanillic acid to yield veratric acid.     

Description of toluene inhibition of methyl bromide biodegradation in seawater and isolation of a marine toluene oxidizer that degrades methyl bromide

Methyl bromide (CH3Br) and methyl chloride (CH3Cl) are important precursors for destruction of stratospheric ozone, and oceanic uptake is an important component of the biogeochemical cycle of these methyl halides. In an effort to identify and characterize the organisms mediating halocarbon biodegradation, we surveyed the effect of potential cometabolic substrates on CH3Br biodegradation using a 13CH3Br incubation technique. Toluene (160 to 200 nM) clearly inhibited CH3Br and CH3Cl degradation in seawater samples from the North Atlantic, North Pacific, and Southern Oceans. Furthermore, a marine bacterium able to co-oxidize CH3Br while growing on toluene was isolated from subtropical Western Atlantic seawater. The bacterium, Oxy6, was also able to oxidize o-xylene and the xylene monooxygenase (XMO) pathway intermediate 3-methylcatechol. Patterns of substrate oxidation, lack of acetylene inhibition, and the inability of the toluene 4-monooxygenase (T4MO)-containing bacterium Pseudomonas mendocina KR1 to degrade CH3Br ruled out participation of the T4MO pathway in Oxy6. Oxy6 also oxidized a variety of toluene (TOL) pathway intermediates such as benzyl alcohol, benzylaldehyde, benzoate, and catechol, but the inability of Pseudomonas putida mt-2 to degrade CH3Br suggested that the TOL pathway might not be responsible for CH3Br biodegradation. Molecular phylogenetic analysis identified Oxy6 to be a member of the family Sphingomonadaceae related to species within the Porphyrobacter genus. Although some Sphingomonadaceae can degrade a variety of xenobiotic compounds, this appears to be the first report of CH3Br degradation for this class of organism. The widespread inhibitory effect of toluene on natural seawater samples and the metabolic capabilities of Oxy6 indicate a possible link between aromatic hydrocarbon utilization and the biogeochemical cycle of methyl halides.     

Chemical models for cytochrome P450 as a biomimetic metabolic activation system in mutation assays

DNA damage is a critical factor in carcinogenesis. The Ames assay is a short-term test that screens for DNA-damaging agents. To be detected in the assay, most carcinogens require oxidation by cytochrome P450, a component of the liver homogenate preparation (S9 mix) that is traditionally used to metabolize promutagens to an active form in vitro. A combination of iron(III) porphyrin plus an oxidant activates many promutagens by mimicking cytochrome P450 metabolism. We previously reported that the mutagenicity of the N-nitrosodialkylamines was detected following reaction with tetrakis(pentafluorophenyl)porphyrinatoiron(III) chloride (Fe(F(5)P)Cl) plus tert-butyl hydroperoxide (t-BuOOH), which yielded the same alcohols and aldehydes as the enzymatic reaction. In the present study, to extend the scope of biomimetic models, we tested the mutagenicity of other carcinogens exposed to chemical oxidation systems.We investigated the optimal assay conditions for the models in Salmonella typhimurium TA1538, a strain sensitive to frame-shift mutagens. We activated 2-aminofluorene (AF), benzo[a]pyrene (B[a]P), a tryptophane pyrolysate 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), and 2-acetylaminofluorene (AAF) with Fe(F(5)P)Cl plus an oxidant-t-BuOOH, m-chloroperoxybenzoic acid (mCPBA), or magnesium monoperoxyphthalate (MPPT)-and we noted the effect of three solvents-acetonitrile (CH(3)CN),1,4-dioxane, and N,N-dimethylformamide (DMF)-on AF activation.All the promutagens became mutagenic in the presence of Fe(F(5)P)Cl plus an oxidant, with the effectiveness of the oxidant varying with the chemical. Aromatic amines, for example, showed the strongest mutagenicity with t-BuOOH whereas polycyclic hydrocarbons showed the strongest mutagenicity with mCPBA. All the promutagens were mutagenic in the presence of Fe(F(5)P)Cl plus MPPT. For AF activation, the order of effectiveness of the solvents was CH(3)CN>1,4-dioxane>DMF. The results suggested that these systems would serve as useful models for microsomal activating systems.     

Intraduplex Photo-cross-linking of p-Azidoaniline Residue and Amino Acid Side Chains Linked to the Complementary Oligonucleotides via a New Phosphorylating Intermediate Formed in the Mukaiyama System

Abstract

Oligonucleotide derivatives carrying a side chain of either lysine or histidine at the 3′-end and their complementary oligonucleotides having photoreactive groups a p-azidophenyl-NH(CH2)_nNH- (n = 4, 6) residue at the 5′-end were prepared by using new phosphorylating species formed by treatment of oligonucleotides with Ph3P and (PyS)₂ or (PyrS)₂. in DMF, DMSO or their mixture. Efficient cross-linking of duplexes occurred under UV-irradiation (λ > 300 nm).     

The potential role of nitric oxide in substrate switching in eosinophil peroxidase

Eosinophil recruitment and enhanced nitric oxide (NO) production are characteristic features of asthma and other airway diseases. Eosinophil peroxidase (EPO), a highly cationic hemoprotein secreted by activation of eosinophils, is believed to play a central role in host defense against invading pathogens. The enzyme uses hydrogen peroxide (H2O2) and bromide (Br-), a preferred cosubstrate of EPO, to generate the cytotoxic oxidant hypobromous acid. The aim of this work was to determine whether NO can compete with plasma levels of Br- and steer the enzyme reaction from a 2e- oxidation to a 1e- oxidation pathway. Rapid kinetic measurements were utilized to measure the rate of EPO compounds I and II formation, duration, and decay at 412 and 432 nm, respectively, at 10 degrees C. An EPO-Fe(III) solution supplemented with increasing Br- concentrations was rapidly mixed with fixed amounts of H2O2 in the absence and in the presence of increasing NO concentrations. In the absence of NO, EPO-Fe(III) primarily converted to compound I and, upon H2O2 exhaustion, it decayed rapidly to the ferric form. NO caused a significant increase in the accumulation of EPO compound II, along with a proportional increase in its rate of formation and duration as determined by the time elapsed during catalysis. The time courses for these events have been incorporated into a comprehensive kinetic model. Computer simulations carried out supported the involvement of a conformational intermediate in the EPO compound II complex decay. Collectively, our results demonstrated that NO displays the potential capacity to promote substrate switching by modulating substrate selectivity of EPO.     

Genetic control of methyl halide production in Arabidopsis

Methyl chloride (CH(3)Cl) and methyl bromide (CH(3)Br) are the primary carriers of natural chlorine and bromine, respectively, to the stratosphere, where they catalyze the destruction of ozone, whereas methyl iodide (CH(3)I) influences aerosol formation and ozone loss in the boundary layer. CH(3)Br is also an agricultural pesticide whose use is regulated by international agreement. Despite the economic and environmental importance of these methyl halides, their natural sources and biological production mechanisms are poorly understood. Besides CH(3)Br fumigation, important sources include oceans, biomass burning, tropical plants, salt marshes, and certain crops and fungi. Here, we demonstrate that the model plant Arabidopsis thaliana produces and emits methyl halides and that the enzyme primarily responsible for the production is encoded by the HARMLESS TO OZONE LAYER (HOL) gene. The encoded protein belongs to a group of methyltransferases capable of catalyzing the S-adenosyl-L-methionine (SAM)-dependent methylation of chloride (Cl(-)), bromide (Br(-)), and iodide (I(-)) to produce methyl halides. In mutant plants with the HOL gene disrupted, methyl halide production is largely eliminated. A phylogenetic analysis with the HOL gene suggests that the ability to produce methyl halides is widespread among vascular plants. This approach provides a genetic basis for understanding and predicting patterns of methyl halide production by plants.