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At least 1,495 records · Page 83Linked to original sources
PubMed2006

Transition state effects in the acid-catalyzed hydrolysis of 5-methoxyacenaphthylene 1,2-oxide: implications for the mechanism of acid-catalyzed hydrolysis of cyclopenta[cd]pyrene 3,4-oxide.

5-Methoxyacenaphthylene 1,2-oxide (5) was synthesized by the reaction of 5-methoxyacenaphthylene with dimethyldioxirane. The rates and products from the acid-catalyzed and pH-independent reactions of 5 in 50:50 dioxane/water have been determined. The half-life of the pH-independent reaction of this very reactive epoxide in 50:50 dioxane/water is only 22 s. Acid-catalyzed hydrolysis of 5 in 50:50 dioxane/water yields 62% of cis diol 6, 37% of trans diol 7, and approximately 1% of 5-methoxy-1,2-dihydroacenaphthylen-1-one (8). The pH-independent reaction of 5 yields mostly ketone 8 (94%), along with minor amounts of cis and trans diols. The relative stabilities of cis and trans diols 6 and 7 were determined by treating either cis or trans diol with perchloric acid in water solutions and following the approach to an equilibrium cis/trans diol mixture as a function of time. At equilibrium, the ratio of cis and trans diols is 19:81, which establishes that trans diol 7 is more stable than cis diol 6. The acid-catalyzed hydrolysis of epoxide 5 therefore yields the less stable cis diol as the major product. It is concluded that transition state effects therefore selectively stabilize the transition state for attack of water on the intermediate carbocation leading to the less stable cis diol. These results suggest that transition state effects are also responsible for formation of the major cis diol in the acid-catalyzed hydrolysis of cyclopenta[cd]pyrene 3,4-oxide, which has a cyclopenta-fused ring similar to that in 5.

Acenaphthenes↗
PubMed1999

Wheat-germ aspartate transcarbamoylase: revised purification, stability and re-evaluation of regulatory kinetics in terms of the Monod-Wyman-Changeux model.

A revised and simplified purification scheme for aspartate transcarbamoylase (ATCase) from wheat-germ is reported, with an eightfold increase in scale (yielding approximately 10 mg of the pure protein from 4 kg of wheat-germ), and improved characteristics of stability and regulatory kinetics. The ATCase obtained is greater than 96% pure, as judged by polyacrylamide gel electrophoresis. The long-term stability (i.e. on a time-scale of several hours to weeks) of the activity of the purified enzyme, under various storage conditions, was investigated. At 4 degreesC and pH 7.5, stability was found to be strongly dependent on protein concentration (increased stability at high concentration), buffer concentration (decreased stability at high buffer concentration) and the inclusion of glycerol (increased stability with increasing glycerol concentration). The enzyme is routinely stored at 4 degreesC, in 0. 05 m Tris/HCl buffer containing 25% glycerol and at high protein concentration (approximately 1 mg.mL-1, or 10 microm in trimers). Under these conditions, the half-life of the enzyme activity is greater than 300 days. Over the time-scale of kinetic experiments (up to 20 min), the diluted activity (at around 1 nm of ATCase, in the presence of ligands) is completely stable. The specific activity remains constant in the range 0.1-10 nm, in the absence and presence of ligands, showing that dissociation of the trimeric enzyme into its subunits is negligible. Steady-state kinetics were examined using the enzyme at a concentration of 1.3 nm. Initial-rate curves for both allosteric ligands, carbamoylphosphate (CP) and uridine 5'-monophosphate (UMP), showed pronounced sigmoidicity, each in the presence of the other. In the absence of UMP, initial-rate curves for CP are hyperbolic. The initial rate data fit reasonably well to a trimeric Monod-Wyman-Changeux model, suggesting a two-state conformational mechanism, greatly favouring the active (R) state when both ligands are absent, in which the R-state binds CP exclusively (dissociation constant = 23.2 microm), and the T-state binds UMP exclusively (dissociation constant = 0.49 microm). This regulatory behaviour was found to be quite stable, and was indistinguishable from that of the enzyme in a freshly made crude extract, even after storage of the pure sample for 5 months. This enzyme preparation is therefore free of the anomalous allosteric kinetics produced by a previous purification scheme, in which the affinity for UMP was markedly reduced, CP rate curves showed no sigmoidicity, while UMP rate curves had sigmoidicity exaggerated by a low maximum.

Allosteric Regulation↗
PubMed2006

Carbon-oxygen bond cleavage with eta9,eta5-bis(indenyl)zirconium sandwich complexes.

Treatment of the eta9,eta5-bis(indenyl)zirconium sandwich complex, (eta9-C9H5-1,3-(SiMe3)2)(eta5-C9H5-1,3-(SiMe3)2)Zr, with dialkyl ethers such as diethyl ether, CH3OR (R=Et, nBu, tBu), nBu2O, or iPr2O resulted in facile C-O bond scission furnishing an eta5,eta5-bis(indenyl)zirconium alkoxy hydride complex and free olefin. In cases where ethylene is formed, trapping by the zirconocene sandwich yields a rare example of a crystallographically characterized, base-free eta5,eta5-bis(indenyl)zirconium ethylene complex. Observation of normal, primary kinetic isotope effects in combination with rate studies and the stability of various model compounds support a mechanism involving rate-determining C-H activation to yield an eta5,eta5-bis(indenyl)zirconium alkyl hydride intermediate followed by rapid beta-alkoxide elimination. For isolable eta6,eta5-bis(indenyl)zirconium THF compounds, thermolysis at 85 degrees C also resulted in C-O bond cleavage to yield the corresponding zirconacycle. Both mechanistic and computational studies again support a pathway involving haptotropic rearrangement to eta5,eta5-bis(indenyl)zirconium intermediates that promote rate-determining C-H activation and ultimately C-O bond scission.

Carbon↗
PubMed2003

Immobilization of glutathione-s-transferase within cross-linked gelatin cylindrical molds.

Rabbit liver cytosolic glutathione-s-transferase (GSTs; EC: 2.5.1.18) was immobilized in cross-linked gelatin cylindrical molds which the formaldehyde was used as cross linker. Glutathione-s-transferases are the enzymes that catalyze the conjugation of wide variety of electrophilic substrates with glutathione. This process generally leads to the detoxification of the xenobiotics. Characterization of immobilized GST was made by using 1-chloro-2,4-dinitrobenzene(CDNB) as substrate. Immobilization efficiency of the enzyme was calculated in terms of activity yield. Optimal enzyme, gelatin and formaldehyde amounts, optimum pH and temperature, Km[CDNB], Km[GSH] and thermal stability was searched and compared with the free enzyme. Furthermore, for studying the detoxification by conjugation in vitro, immobilized GST was tested using stirred batch reactor system and found suitable with a high yield of 2,4-dinitrophenyl-GSH conjugate formation.

Animals↗
PubMed1999

Structure-based conformational preferences of amino acids.

Proteins can be very tolerant to amino acid substitution, even within their core. Understanding the factors responsible for this behavior is of critical importance for protein engineering and design. Mutations in proteins have been quantified in terms of the changes in stability they induce. For example, guest residues in specific secondary structures have been used as probes of conformational preferences of amino acids, yielding propensity scales. Predicting these amino acid propensities would be a good test of any new potential energy functions used to mimic protein stability. We have recently developed a protein design procedure that optimizes whole sequences for a given target conformation based on the knowledge of the template backbone and on a semiempirical potential energy function. This energy function is purely physical, including steric interactions based on a Lennard-Jones potential, electrostatics based on a Coulomb potential, and hydrophobicity in the form of an environment free energy based on accessible surface area and interatomic contact areas. Sequences designed by this procedure for 10 different proteins were analyzed to extract conformational preferences for amino acids. The resulting structure-based propensity scales show significant agreements with experimental propensity scale values, both for alpha-helices and beta-sheets. These results indicate that amino acid conformational preferences are a natural consequence of the potential energy we use. This confirms the accuracy of our potential and indicates that such preferences should not be added as a design criterion.

Amino Acids↗
PubMed2006

Cell evolution and Earth history: stasis and revolution.

This synthesis has three main parts. The first discusses the overall tree of life and nature of the last common ancestor (cenancestor). I emphasize key steps in cellular evolution important for ordering and timing the major evolutionary innovations in the history of the biosphere, explaining especially the origins of the eukaryote cell and of bacterial flagella and cell envelope novelties. Second, I map the tree onto the fossil record and discuss dates of key events and their biogeochemical impact. Finally, I present a broad synthesis, discussing evidence for a three-phase history of life. The first phase began perhaps ca 3.5 Gyr ago, when the origin of cells and anoxic photosynthesis generated the arguably most primitive prokaryote phylum, Chlorobacteria (= Chloroflexi), the first negibacteria with cells bounded by two acyl ester phospholipid membranes. After this 'chlorobacterial age' of benthic anaerobic evolution protected from UV radiation by mineral grains, two momentous quantum evolutionary episodes of cellular innovation and microbial radiation dramatically transformed the Earth's surface: the glycobacterial revolution initiated an oxygenic 'age of cyanobacteria' and, as the ozone layer grew, the rise of plankton; immensely later, probably as recently as ca 0.9 Gyr ago, the neomuran revolution ushered in the 'age of eukaryotes', Archaebacteria (arguably the youngest bacterial phylum), and morphological complexity. Diversification of glycobacteria ca 2.8 Gyr ago, predominantly inhabiting stratified benthic mats, I suggest caused serial depletion of 13C by ribulose 1,5-bis-phosphate caboxylase/oxygenase (Rubisco) to yield ultralight late Archaean organic carbon formerly attributed to methanogenesis plus methanotrophy. The late origin of archaebacterial methanogenesis ca 720 Myr ago perhaps triggered snowball Earth episodes by slight global warming increasing weathering and reducing CO2 levels, to yield runaway cooling; the origin of anaerobic methane oxidation ca 570 Myr ago reduced methane flux at source, stabilizing Phanerozoic climates. I argue that the major cellular innovations exhibit a pattern of quantum evolution followed by very rapid radiation and then substantial stasis, as described by Simpson. They yielded organisms that are a mosaic of extremely conservative and radically novel features, as characterized by De Beer's phrase 'mosaic evolution'. Evolution is not evenly paced and there are no real molecular clocks.

Archaea↗
PubMed1991

Heterologous protein production by filamentous fungi.

There are clearly many facets to successful production of heterologous proteins from filamentous fungi. The objectives are to exploit the natural ability of some species to secrete high levels of protein. The heterologous target proteins produced in a fungal host must be acceptable to the public and be economic to produce, i.e. the targets must be authentic (in structure and activity) and be produced in high yield to necessary levels of purity. The appearance of heterologous products from fungi on the market is testament to some success but, equally, there are considerable limitations in our ability to produce desired yields of many target proteins. We endorse the view of van den Hondel, Punt and van Gorcom (1991) that for the commercial production of heterologous proteins from filamentous fungi more information is required on transcriptional control, introns, mRNA stability and processing, translational efficiency, protein secretion, glycosylation and proteolysis. In addition, there is scope for yield improvement based on a better understanding of the physiology of growth/product secretion coupled to appropriate bioreactor operation. The authenticity of product is an aspect which will assume increasing importance, particularly for therapeutic proteins. The level at which the structures and functional activity of heterologous proteins are assessed will ultimately be determined by legislation. The analytical methods currently available are not always sufficient, for example, to reveal folded structures, and most proteins are not amenable to analysis by two-dimensional NMR. The authenticity of target heterologous proteins will also need to be assessed in relation to the glycosylation level and pattern. This is not easily done and explains the paucity of detailed information published to date on glycosylation of fungal proteins. Novel engineered proteins are already being produced from filamentous fungi where expression is an aid to investigation of structure-function relationships. Commercial production of such engineered proteins will require approval subject to a range of stringently applied tests and analyses. This imposes an even greater need to be able to specify and control, in a rational manner, the structures of recombinant proteins. The research needs for realization of improved yields are equally important in assuring authenticity of product. It is encouraging that progress is being made on all fronts, primarily with Aspergillus spp. and T. reesei, but also with other species, such as N. crassa.

Animals↗
PubMed1994

The effect of cyclodextrins on the stability of peptides in nasal enzymic systems.

Leucine enkephalin (YGGFL) undergoes rapid degradation in sheep nasal mucosa to yield GGFL which is further degraded to FL. The activity of the nasal mucosal homogenate against YGGFL and GGFL (t1/2 12 and 7 min) was significantly greater than that observed with a nasal wash fluid (t1/2 40 and 13 min). The effect of cyclodextrins on the rate of degradation of FGG and YGGFL by leucine aminopeptidase (LAP) and of GGF by carboxypeptidase A (CPA) was monitored. Little effect was observed with FGG (with LAP) but the half-life of YGGFL (with LAP) was extended from approximately 44 min to approximately 75 min in the presence of a 25-fold excess of beta-cyclodextrin. The stability of GGF (with CPA) was also enhanced; an effect was observable with a 5-fold excess of cyclodextrin and the half-life could be extended by 40-75%. An equation is presented which allows the estimation of the concentration of free peptide in the peptide-cyclodextrin solutions.

Animals↗
PubMed1986

Growth Pattern and Yield of a Chemoautotrophic Beggiatoa sp. in Oxygen-Sulfide Microgradients.

Recently developed techniques involving opposed, gel-stabilized gradients of O(2) and H(2)S permit cultivation of a marine Beggiatoa strain as a chemolithoautotroph which uses gliding motility to precisely track the interface between H(2)S and O(2). In the current study with microelectrodes, vertical profiles of H(2), O(2), and pH were measured in replicate cultures grown for various intervals. After an initial period of exponential biomass increase (doubling time, 11 h), linear growth prevailed throughout much of the time course. This H(2)S-limited growth was followed by a transition to stationary phase when the declining H(2)S flux was sufficient only to supply maintenance energy. During late-exponential and linear growth phases, the Beggiatoa sp. consumed a constant 0.6 mol of H(2)S for each 1.0 mol of O(2), the ratio anticipated for balanced lithoautotrophic growth at the expense of complete oxidation of H(2)S to SO(4). Over the entire range of conditions studied, this consumption ratio varied by approximately twofold. By measuring the extent to which the presence of the bacterial plate diminished the overlap of O(2) and H(2)S, we demonstrated that oxidation of H(2)S by Beggiatoa sp. is approximately 3 orders of magnitude faster than spontaneous chemical oxidation. By integrating sulfide profiles and comparing sulfide consumed with biomass produced, a growth yield of 8.4 g (dry weight) mol of H(2)S was computed. This is higher than that found for sulfide-grown thiobacilli, indicating very efficient growth of Beggiatoa sp. as a chemoautotroph. The methods used here offer a unique opportunity to determine the yield of H(2)S-oxidizing chemolithoautotrophs while avoiding several problems inherent in the use of homogeneous liquid culture. Finally, by monitoring time-dependent formation of H(2)S profiles under anoxic conditions, we demonstrate a method for calculating the molecular diffusion coefficient of soluble substrates in gel-stabilized media.

Journal Article↗
PubMed1985

Reversibility of the stabilization effect of sodium molybdate on uterine estrogen and progesterone receptors of the vervet monkey.

Sodium molybdate affected the stability of vervet monkey (Cercopithecus aethiops pygerythrus) uterine estrogen (ER) and progesterone (PR) receptors. Yields of receptors were invariably higher (20-40%) when cytosols were prepared in the presence of 10mM sodium molybdate. No changes were observed in the binding affinities for the natural ligands as reflected in dissociation constants. Receptor-ligand association at 0 degrees C and 20 degrees C was not affected in the presence or absence of molybdate. Stability studies at 37 degrees C indicated both receptors to be more resistant to inactivation in the presence of molybdate. Dissociation of ER and PR was biphasic, indicating the existence of slow (SDC), as well as fast dissociating (FDC) complexes. Rate constants of dissociation were significantly affected by the presence of sodium molybdate. Although no significant changes in the sedimentation coefficients were observed, marked differences in the actual gradient profiles could be illustrated in the presence or absence of sodium molybdate. Observed effects could only be partially reversed in sedimentation dialysis experiments. Proteolytic inhibitors phenylmethylsulfonylfluoride (PMSF) and leupeptin had no inhibitive effect on the molybdate stabilization of ER and PR.

Animals↗
PubMed1992

Inhibition of DNA polymerase activity by thymine hydrates.

Ultraviolet irradiation of DNA results in various pyrimidine modifications. We have demonstrated formation of both cis-thymine hydrate and trans-thymine hydrate (6-hydroxy-5,6-dihydrothymine) in UV-irradiated poly(dA-dT):poly(dA-dT). Both are released from DNA as free bases by bacterial and human glycosylases. Thymine hydrates are stable in DNA and can be detected in control, unirradiated substrates. We examined the effects of thymine hydrates in UV-irradiated substrate poly(dA-dT):poly(dA-dT) on E. coli DNA polymerase I activity. Enzymic incorporation of labeled thymidine-5'-monophosphate significantly decreased with increasing UV dose. Reversal of DNA thymine hydrates to thymines by mild heating of the substrate prior to enzymic reaction resulted in partial recovery of nucleotide incorporation. Cyclobutane thymine dimers are formed between non-adjacent thymines in UV-irradiated poly(dA-dT):poly(dA-dT). These are responsible for the incomplete recovery of DNA polymerase activity following heating due to their heat stability. Analyses of the irradiated and hydrolyzed substrate also demonstrated formation of minor yields of photoproducts formed by covalent linkage of adjacent thymines and adenines by UV-irradiation. Therefore, the thymine hydrates formed in UV-irradiated DNA partially inhibit polymerase activity during DNA synthesis and thus could be potentially lethal if unrepaired.

Chromatography, High Pressure Liquid↗
PubMed1997

Hoechst 33258 Tethered by a Hexa(ethylene glycol) Linker to the 5'-Termini of Oligodeoxynucleotide 15-Mers: Duplex Stabilization and Fluorescence Properties.

A fluorescent Hoechst 33258 derivative has been prepared in which a hexa(ethylene glycol) linker is attached to the terminal phenol residue. Conjugation of this derivative to DNA sequences is accomplished by a reversed coupling protocol, one in which the 5'-terminal nucleoside residue of a fully protected DNA sequence is converted to a terminal phosphoramidite. In the presence of the Hoechst derivative and tetrazole the final coupling reaction is achieved to generate the conjugated nucleic acid. After deprotection and cleavage of the conjugate from the support, HPLC analysis indicates that the conjugation reaction proceeds with yields as high as 75%. The presence of the conjugated Hoechst derivative increases the stability of DNA duplexes typically by 10-16 degrees C. A variety of sequence variants indicate that the tether length is sufficient to reach beyond the terminus of the DNA duplex and bind to internal A-T rich target sequences as far away as four base pairs from the site of attachment. A four base pair binding site appears to be necessary for effective helix stabilization by the conjugate, but in some cases can include a G-C base pair, which is consistent with a previous X-ray diffraction study regarding the binding of Hoechst 33258 to duplex DNA. When A-T base pairs alternate with G-C base pairs, a small but discernible increase is T(m) is observed (3.6 degrees C), indicating that binding to this sequence still occurs, but not in the same manner as to A-T rich sequences. Upon formation of the conjugated duplex, an enhanced quantum yield for the fluorescence emission spectrum of the tethered Hoechst derivative is observed. When an A-T rich binding site is present, the enhanced quantum yield increases by at least 16- and in some cases to nearly 30-fold relative to the value obtained for the single-stranded DNA-Hoechst conjugate.

Journal Article↗
PubMed2002

Novel use of a guanosine prodrug approach to convert 2',3'-didehydro-2',3'-dideoxyguanosine into a viable antiviral agent.

Transient kinetic studies with human immunodeficiency virus (HIV) type 1 reverse transcriptase suggest that nucleotide analogs containing the 2',3'-didehydro-2',3'-dideoxy ribose ring structure present in D4T (stavudine) triphosphate are among the most effective alternative substrates. For unclear reasons, however, the corresponding purine nucleoside, 2',3'-didehydro-2',3'-dideoxyguanosine (D4G), was found to be inactive in cell culture. We have found that the previously reported lack of activity of D4G is primarily due to solution instability, and in this report we describe a novel use of a guanosine prodrug approach to stabilize the nucleoside. D4G was modified at the 6 position of the purine ring to contain a cyclopropylamino group yielding the prodrug, cyclo-D4G. An evaluation of cyclo-D4G revealed that the prodrug possessed anti-HIV activity. In addition, cyclo-D4G had increased stability, lipophilicity, and solubility, as well as decreased toxicity relative to D4G, suggesting that further study is warranted.

Anti-HIV Agents↗
PubMed1988

Salt dependence of DNA structural stabilities in solution. Theoretical predictions versus experiments.

The predictions of currently available theories for treating DNA-diffuse ionic cloud free energy contributions to conformational stability have been tested against experimental data for salt induced B-Z and B-A transitions. The theories considered are (i) Manning's counterion condensation approach (CC), (ii) the idealized Poisson-Boltzmann approximation (PB), and (iii) the potentials of mean force (PMF) approach proposed by Soumpasis. As far as we can judge from comparison with the set of experimental data currently available, it is found that only the latter theory yields satisfactory quantitative results for the dependence of the B-Z and B-A relative stabilities on monovalent salt concentration. The correct application of the PB and CC theories does not yield very low salt Z-B transitions, in contradiction to earlier assertions. At low salt concentrations the PB theory is qualitatively correct in predicting that the B form is electrostatically more favorable than both the A and Z forms, whereas the CC theory is qualitatively wrong predicting that Z-DNA is more stable than both B and A DNA.

DNA↗
PubMed1983

Approaches to the synthesis of retro-inverso peptides.

Partial retro-inverso modification of biologically active peptides is described as a topochemical alteration of the backbone to prevent enzymatic degradation. The preparation of gem-diaminoalkyl residues from peptide amides using the reagent [bis(trifluoroacetoxy)iodo]benzene (TIB) is discussed. Treatment of N-t-butyloxycarbonyl tyrosine and N-t-butyloxycarbonyl tryptophan with this reagent led to decomposition of the protected amino acids. Protecting the tyrosine and tryptophan residues by t-butyl ether and Nin-formyl groups, respectively, prevented decomposition and led to good yields of the desired products. Racemic 2-alkylmalonyl diastereomers were found to be separable by HPLC. The chiral stability of peptides containing optically active malonyl residues was investigated under simulated physiological conditions. Synthetic considerations for the incorporation of gem-diaminoalkyl and 2-alkylmalonyl residues into larger peptides to yield partially modified retro-inverso peptide analogs are presented.

Amino Acid Sequence↗
PubMed2002

Hydrolysis of lactose by beta-glycosidase CelB from hyperthermophilic archaeon Pyrococcus furiosus: comparison of hollow-fiber membrane and packed-bed immobilized enzyme reactors for continuous processing of ultrahigh temperature-treated skim milk.

Recombinant beta-glycosidase CelB from the hyperthermophilic archaeon Pyrococcusfuriosus was produced through expression of the plasmid-encoded gene in Escherichia coli. Bioreactor cultivations of E. coli in the presence of the inductor isopropyl-1-thio-beta-D-galactoside (0.1 mM) gave approx 100,000 U of enzyme activity/L of culture medium after 8 h of growth. A technical-grade enzyme for the hydrolysis of lactose was prepared by precipitating the mesophilic protein at 80 degrees C. A hollow-fiber membrane reactor was developed, and its performance during continuous processing of ultrahigh temperature-treated (UHT) skim milk at 70 degrees C was analyzed regarding long-term stability, productivity, and diffusional limitation thereof. CelB was covalently attached onto Eupergit C in yields of 80%, and a packed-bed immobilized enzyme reactor was used for the continuous hydrolysis of lactose in UHT skim milk at 70 degrees C. The packed-bed reactor was approximately 10-fold more stable and gave about the same productivity at 80% substrate conversion as the hollow-fiber reactor at 60% substrate conversion. The marked difference in the stability of free and immobilized CelB seems to reflect mainly binding of the soluble enzyme to the membrane surface of the hollow-fiber module. Under these bound conditions, CelB is essentially inactive. CelB is essentially inactive. Microbial contamination of the reactors did not occur during reaction times of up to 39 d, given that UHT skim milk and not pasteurized skim milk was used as the substrate.

Animals↗
PubMed2002

Kinetic theory of symmetry-dependent strength in carbon nanotubes.

Carbon nanotubes yield to mechanical force by a primary dislocation dipole whose formation energy describes the thermodynamic stability of the tubule. However, the real-time strength is determined by the rate of defect formation, defined in turn by the activation barrier for the bond flip. First extensive computations of the kinetic barriers for a variety of strain-lattice orientations lead to predictions of the yield strength. Its value depends on nanotube chiral symmetry, in a way very different from the thermodynamic assessment.

Journal Article↗
PubMed1982

Assessment of solvents for the recovery of nitroglycerine from hands using cotton swabs.

Eight solvents were compared for their relative efficiency in removing nitroglycerine from the hands of persons handling explosives. The amount of interfering material also removed from the hands by the cotton swabs and the stability of the nitroglycerine in the solvent used were also investigated. Aqueous solvents yielded the best recoveries, when the extracts were partially purified by thin-layer chromatography before analysis, but the explosive was degraded rapidly by microorganisms that grew in the solutions. Of the aqueous, organic, and polar solvents tested, ethanol was found to offer the most complete, consistent, and stable recovery.

Drug Stability↗