bluuebunny/crossref_metadata_2025 huggingface dataset:
Processing of Emulsions of Explosive Melts
Authors: Teipel Ulrich
Published: May 2005

In the context of the waste disposal of explosives, generally the suitability of the processing method is of importance. When processing explosives, the choice method of treatment, after having melted out the explosive, is to emulsify the aqueous solution of the melt for the purpose of disposing the emulsified explosives by subsequent emulsions the first aim is to produce a multiple phase system consisting of two components that are practically immiscible. For this purpose, emulsifying machines that work according to the rotational‐stationary principle are used. Colloid millsm, for instance, employ the viscous tensions in the laminar flow field to disrupt the droplets. Gear‐ring dispersing machines, on teh other hand, will cause a disruption oif the droplets by turbulent eddies. In this work the emulsifying equipment along with the mechanisms of drop deformation with subsequent disruption will be trated.
Co‐Precipitation Studies on Lead Azide with Tetrazole Derivatives‐a search for lead azide substitute
Authors: Om Redddy G.
Published: May 2005

Co‐precipitation of lead azide with various tetrazole and nitrophenol derivatives is discussed. Thermal behaviour of lead azide before and after co‐precipitation is studied suing DSC. Thermal study indicated that the co‐precipitation of lead azide with other flame sensitive compounds produced an intimate mixture of lead azide and lead salts of tetrazole and nitrophenyl derivatives but not a single compounds.

Explosive properties evaluation indicated that the co‐precipitation process not only improves the flame sensitivity of lead azide but also eliminates the hazardous process of physical mixing of lead azide with flame sensitive materials. A good correlation between thermal sensitivity and flame sensitivity is noticed. Both thermal and flame sensitivity decreases.
Origine physique des Points chauds dans les compositions explosives pressées au TATB
Authors: Castille C. , Germain E. , Belmas R.
Published: May 2005

Nous identifions, par une étude expérimentale et théorique, l'orgine physique des points chauds dans les compositions explosives pressées, au TATB, à liants inertes. Nous quantifions ainsi l'influence de la porosité, du liant, des gaz occlus dans les pores, des phénomènes d'écrasement hydrodynamiques et des déformations viscoplastiques de l'explosif.
Study on Thermal Decomposition of Pentolites by modified vacuum stability apparatus and differential scanning calorimetry
Authors: Huang Chen‐Chia , Ger Ming‐Der , Chen Sun‐I
Published: May 2005

A modified manometric vacuum stability test (VST) apparatus as well as a differential scanning calorimeter (DSC) were used to study the decomposition of pentolites (mixtures of PETN and TNT). The former operated isothermally at three heating temperatures (100°.C 110°C and 120°C), the latter with a constant heating rate. Various compositions of pontolites were examined. For the VST tests, heating periods were 40 hours except for experiments in which resulting pressures were higher than 760 mmHg. Using the ideal gas law, the volume of gaseous products was calculated from the pressure readings. The evolved gas volume from pentolites tested at 100°C is about as large as that from either pure PETN or pure TNT. However, the gas volumes released from pentolites heated at 110°C and 120°C are apparently larger than those from either PETN or TNT alone. In particular, a mixture of PETN and TNT with a 1:1 weight ratio releases a maximum volume of gas products. It is found by DSC analyses that decompositions temperature of TNT decreases as mixed with PETN.
Thermal Decomposition of Energetic Materials 57. Products of some self‐igniting fuel‐HNO3 Systems
Authors: Patil D. G. , Jain S. R. , Brill T. B.
Published: May 2005

Exothermic reactions of some self igniting fuel‐HNO3 systems have been examined by the rapid‐scan FIR/thermal profiling technique. A sudden rise in temperature is observed when the liquid oxidizer is dropped onto the solid fuel. Simultaneous monitoring of the gas products of the reaction occurring between p‐phenylenediamine and HNO3 reveals the formation of Co2, NO2 and HONO. Immediate evolution of NO2 is observed in the synergistically igniting systems comprised of substituted anilines, Mg and HNO3. Thiocarbohydrazide and its acetone and benzaldehyde monoderivatives on reacting with HNO3 produce SO2, NO2 and, possibly, OCS. The results are explained in terms of the oxidation and nitration reactions occurring in these systems.
Energetic Materials Research at HSE's explosion and flame laboratory
Authors: Thomson B. J.
Published: May 2005

The UK Health and Safety Executive's (HSE) Explosion and Flame Laboratory in buxton has its roots in coal‐mining safety, undertaking research into mining explosives in 1926. But today, in support of the HSE's duties across a wise range of industries, energetic materials research at Buxton covers testing, detonation, chemical analysis, thermal stability, blast characteristics, characterization, classification, thermal radiation and deflagration studies encompassing mining and commercial explosives and energetic and self‐reactive substances. International collaboration occurs on a number of fronts and is increasingly sought in pursuing HSE's aims in safety promotion.
The Mechanical Sensitiveness of Titanium/Blackpowder pyrotechnic compositions
Authors: Wharton R. K. , Rapley R. J. , Harding J. A.
Published: May 2005

Titanium/blackpowder compositions have been involved in a number of ignition incidents during consolidation. We report the results of a systematic study to investigate the effects of the particle size and proportion of titanium on the mechanical sensitiveness of such mixtures. Our results indicate that the compositions are sensitive to both impact and friction stimuli and that the forms of the dependence on titanium content are different. Mixtures of blackpowder with 20%–30% titanium have been shown to be particularly friction sensitive. We have also found that the sensitiveness of titanium/blackpowder compositions to mechanical forces is independent of the particle size of titanium over the range investigated in this study.
Synthesis and Characterization of Methylnitramino‐Substituted pyridines and triazines
Authors: Ritter Helmut , Licht Hans H.
Published: May 2005

Four new explosives with heteroaromatic structure were obtained by methylaminolysis of suitable intermediates and subsequent nitration: 2‐methylnitramino‐3,5‐dinitropyridine (2‐MNP), the isomeric 4‐methylnitramino‐3,5‐dinitropyridine (4‐MNP), the tetranitro compound 2,6‐bis(methylnitramino)‐3,5‐dinitropyridine (2,6‐BMNP) and the triazine derivative 2,4,6‐tris(methylnitramino)‐1,3,5‐triazine (TMNT). This paper describes synthesis, the characterization by IR and NMR spectroscopy, and the thermal behaviour of these compounds. Their density and detonation velocity as well as the results from sensitivity tests are given.
Synthesis of N,N′‐bis(2,4‐dinitrobenzofuroxan)‐1,3,5‐trinitro‐2,6‐diaminobenzene
Authors: Naixing Wang , Boren Chen , Yuxiang Ou
Published: May 2005

N,N′‐bis(2,4‐dinitrobenzofuroxan)‐1,3,5‐trinitro‐2,6‐diaminobenzene (V) has been synthesized from 1,3‐diaminobenzene and trinitrodichlorobenzene. The molecular structure of this compound has been determined by elemental analysis, IR, 1H‐NMR, and MS spectroscopies.
Amorçage par chocs simples et doubles d'une composition mixte TATB‐octogène
Authors: Nicollet M. , Belmas R. , Plotard J. P. , Udiment B. , Leroy M.
Published: May 2005

Une étude de l'amorçage par choc d'une composition mixte TATB/octogène est présentée. Des mesures de pression par jauges manganin sont réalisées, en régime transitoire, suite à des chocs simples ou doubles exercés sur l'explosif par l'impact de projectiles propulsés à l'aide d'un lanceur à poudre. Les résultats obtenus sont interpretés en utilisant un modèle de points chauds développé par ailleurs. Cette analyse montre l'importance de la microstructure de la composition (et en particulier, celle de l'existence de deux types de porosité) pour l'initiation par choc de cette composition.
Study of The Blast Waves from the Explosion of Nonspherical Charges
Authors: Ismail M. M. , Murray S. G.
Published: May 2005

The blast wave patterns from the explosion of cylindrical charges are very complex and the pressure‐time histories exhibit multiple shocks. The accurate assessment of the blast wave parameters (positive peak overpressure, duration, and the positive impulse) thus is not a simple task. In this paper a simple system is described for studying the blast waves from the explosion of small cylindrical charges together with comprehensive methods to analyse the experimental results. The assessment of the near‐field/far‐field behaviour also has been studied.
Segmented Penetrators
Authors: Weihrauch G. , Wollmann E.
Published: May 2005

This paper analyses the terminal ballistic performance of segmented rod penetrators in semi‐infinite, spaced as well as reactive targets. The model scaled projectiles with a mass of about 10 g are launched by a light gas gun of caliber 30 mm at velocities up to 4 km/s. To keep the initial acceleration low enough, the junction between the first and the second stage of the gun was appropriately modified. The projectiles are composed of a series of tungsten alloy segments guided by a thin light metal tube. Between the segments with a L/D‐ratio of one there are cylinders made of plastics or aluminium. Usually the space is in the order of one or two projectile diameters. The perforation power of such segmented rods is compared with two types of homogeneous projectiles of equal mass and velocity. One reference projectile has equal length but lower diameter, the other one has the same diameter but a lower length. Experiments against semi‐inifite targets show an increase in penetration depth of about 20 %, compared with homogeneous projectiles of the same diameter. This advantage vanishes if the reference projectile has equal length. In the four‐plate target as well as in the reactive armour, segmented rods are significantly less efficient due to their low stiffness and greater length.
Theoretical Analysis of the Penetration Performance of experimentally measured shaped charge jets
Authors: Heider N.
Published: May 2005

The cratering process of a shaped charge jet is a complex phenomenon because the jet consists of a series of discrete particles that create separate craters within the target. The cumulative effects taking into account the contribution of all jet particles give the final penetration performance. For a theoretical analysis of the terminal ballistic performance of shaped charge jets, it is therefore necessary to measure experimentally the complete three‐dimensional motion of each jet particle. This can only be done by sophisticated techniques like for example Double‐Orthogonal Synchro‐Streak (DOSST) introduced by Held. Data from such experiments can be used as input for penetration models to calculate the penetration depths of jets. The model used for this analysis includes a description of the crater shape together with an appropriate selection algorithm to find the impact position of a single jet particle within the already formed crater profiles. The calculated values for the penetration performance are compared with the data provided by DOSST experiments from Held.
Research and development in the area of explosively formed projectiles charge technology
Authors: Weimann Klaus
Published: May 2005

Results of experimental investigations of the influence of charge length and confinement on the velocity, form and terminal ballistic performance of explosively formed projectiles are presented. In order to make quite sure that the projectile shows no asymmetries, a new technique was developed to form projectiles with “star‐shaped tail”.
Comparative characteristics of some experimental and computational methods for estimating Impact Sensitivity Parameters of Explosives
Authors: Afanas'Ev German T. , Pivina Tatyana S. , Sukhachev Dimitrii V.
Published: May 2005

This article presents some theoretical and experimental methods for estimating parameters of impact sensitivity. Possible relationships between the structures of compounds and the parameters characterizing the sensitivity of explosives to mechanical impact are analyzed.
Energy Output of Insensitive High Explosives by measuring the detonation products
Authors: Volk F. , Schedlbauer F.
Published: May 2005

The detonation products of high explosives are dependent on pressure and also on the confinement under which the detonation reaction proceeds. To determine the detonation products of less‐sensitive high explosives, such as TNT/nitroguanidine (NQ) and PBX charges with polybutadiene (PB) binder containing RDX together with or without aluminium (Al), experiments have been performed in a stainless steel chamber with a volume of 1.5 m3. These experiments were done under different ambient argon pressures up to 0.3 MPa. Gaseous reaction products were analysed by mass spectrometry and chemiluminescence analysis. Solid reaction products were analyzed measuring the carbon residue or the unreacted aluminium. It was found that the detonation products were highly dependent on the ambient pressure of argon. The most important changes of the reaction products and therefore also of the energy output were found between vacuum and atmospheric pressure of argon. With increasing pressure, H2 and CO decrease and CO2, H2O, Cs, NH3, HCN and CH4 increase together with the reaction enthalpy. By analysing the physical structure of the carbon residue, diamonds have been observed between 4 nm and 7 nm in diameter.
Considerations about the Analytical Modelling of Shaped Charges
Authors: Chanteret Pierre Yves
Published: May 2005

The problem of building and using analytical codes for shaped charge simulation is reviewed. The basic physics of the whole shaped charge functioning is considered, starting from explosive liner interaction, going through jet formation and jet break‐up, down to cratering into the target. For each stage of the phenomenon, a critical look is given to the existing analytical models, with the idea of determining which models are able to adequately predict the shaped charge behavior with keeping an as low as possible degree of complexity. On reviewing these analytical models, it is shown that some parameters have to be taken into account for a better understanding of what governs shaped charge performance.
Influence of Transverse Air or Inert‐Filled Gaps in HE Charges on the detonation velocity
Authors: Held Manfred
Published: May 2005

Gaps 0.8‐mm wide and transverse to the direction of detonation in high‐performance high explosive compositions, such as squeeze cast TNT/HMX (15/85) or pressed HMX/B (97/3), show no measurable time delay, or it must be less than 50 ns. As expected, delay times increase with the gap width. A surprising result, however, is the convex shape of the time delay curves, which begins at a gap width of about 1 mm. The delay time curves from air and plexiglass‐filled gaps resemble one another very much.
Electric Spark and ESD Sensitivity of Reactive Solids (primary or secondary explosive, propellant, pyrotechnics). Part II: Energy transfer mechanisms and comprehensive study on E50
Authors: Auzanneau Max , Roux Michel
Published: May 2005

The energy transfer mechanism from the electric spark to the reactive solid sample in powder form has been determined. Only a small portion of the solid is heated to the explosion critical temperature through a resistive heating by electric current. In fact, hot spots develop at the thinnest part of the solid, i.e. at intergrain contact points.

We studied the evolution of thermal diffusivity and of sensitivity to electric spark as a function of powdered HMX granulometry. It allowed us to specify the respective importance of the grain size and shape in this evolution.
Simple Calculation Methods for Munitions Cookoff times and temperatures
Authors: Victor Andrew C.
Published: May 2005

Simple one‐dimensional quasi‐static heat transfer calculations can be used to estimate fast cookoff times of cylindrical munitions with metal cases. The most critical parameter for the thermal analysis is the heat flux to the ordnance from the fire. One must remain aware that heating will be different for transparent flames of propane or methane test fires than they are for the opaque smoky flames of wood and jet‐fuel fires. Good values for material thermal conductivities and energetic material ignition behavior are also needed. Low‐conductivity composite cases cannot be analyzed in the same way because case mechanical failure is the primary initial failure path, rather than thermal conduction leading directly to ignition of the energetic material. Reaction violence cannot be calculated in a simple way with the present state of the art.

Simple hand analysis of slow cookoff problems is limited to simple symmetric shapes of the type that were published over 30 years ago involving constant boundary temperatures. Modern computers, using finite‐difference codes can be used to readily solve problems with varying boundary temperatures to predict time to cookoff. However, as this paper shows, quasi‐static solutions of symmetric shapes (slabs, cylinders and spheres) can be obtained with desktop computer spreadsheets that give the same results as the finite‐difference codes. There are no a priori methods for predicting the violence of the slow cookoff reaction. These same comments apply as well to intermediate cookoff heating rates (greater than 3.3 K/h).

Calculations by the methods of this paper place tools for designing experiments to explore cookoff behavior and for designing ordnance to meet insensitive munitions requirements on virtually every desktop.
Characterization of the Zirconium/Potassium Perchlorate/Nitrocellulose pyrotechnic system by simultaneous thermogravimetry‐differential thermal analysis‐mass spectrometry
Authors: Berger B. , Charsley E. L. , Warrington S. B.
Published: May 2005

Simultaneous thermogravimetry‐differential thermal analysis‐mass spectrometry have been used to characterize the zirconium/potassium perchlorate/nitrocellulose pyrotechnic system, by examining the components and their binary and ternary combinations under inert atmosphere conditions. Zirconium and potassium perchlorate were found to give an exothermic solid state reaction between 300°C and 500°C and the reaction was influenced significantly by the presence of small amounts of nitrocellulose. The decomposition of unreacted potassium perchlorate was observed to commence in the latter stages of the reaction and was found to be catalyzed by presence of the reaction products ZrO2 and KCl.
Reactions of TATB‐Based Explosive with Molten Metal
Authors: Maienschein Jon L. , Nichols Albert L. , Wardell Jeffrey F.
Published: May 2005

The reactions of combustion products (CO, H2O) from the insensitive high explosive LX‐17 (92.5 wt% 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB), 7.5 wt% Kel‐F 800 binder) with molten metal (75 a%Nd, 25 a% Fe) were studied, to determine their contribution to the energy release rate of deflagrating LX‐17, Kinetic data taken with gas mixtures of CO and H2O, and larger‐scale tests with LX‐17, showed that the reactions were slow and incomplete and that there was no significant contribution to the energy release rate. From the tests with JX‐17, the effective flame temperature and burn velocity were dependent on confinement of gas products. LX‐17 preheated to 500 K ‐ 510 K showed effective flame temperatures of 1100 K ‐ 1400 K and burn rates of 0.08–0.11 mm/s, depending on the extent of gas confinement by the molten metal.
Thermal Decomposition of BAMO Copolymers
Authors: Kimura Eishu , Oyumi Yoshio
Published: May 2005

The effects of copolymerization of THF, as an inert component, AMMO, as an energetic one and NMMO, as a nitrate ester, with BAMO on their thermal decomposition are reported here. Although the thermal decomposition of the BAMO and NMMO units in B/N(7/3) carry out independently and the heat generated by the NMMO unit decomposition accelerates the BAMO unit decomposition, the THF and AMMO units do not affect that of the BAMO unit in B/T(7/3) and B/A(7/3). One exothermic peak in DSC is shown for B/A(7/3) and B/T(7/3) except for B/N(7/3) which shows two peaks. One peak at lower temperature is from the NMMO unit decomposition and the other is from the BAMO unit. The rate of decomposition of B/A(7/3) is the same as that of poly(BAMO), which indicates that the reactivity of the AMMO unit is equal to that of the BAMO unit.

In propellant, containing 75% HMX and 25% copolymer binder, burning rate of B/A(7/3)/HMX is faster than that of B/N(7/3)/HMX. Although the heat of decomposition for B/A(7/3) in DSC is smaller than that for B/N(7/3), that of B/A(7/3)/HMX is larger than that of B/N(7/3)/HMX. The reaction occurred in the condensed phase of the propellant, therefore, may play an important role in the combustion.
Numerical calibration of donor systems for some GAP tests
Authors: Hudson Lewis C. , Bernecker Richard R.
Published: May 2005

Numerical models of various donor/attenuator systems utilized in gap tests were evaluated with the DYNA2D hydrocode. Three donor (pressed pentolite)/attenuator (PMMA) configurations were tested. Case I and Case 2 had a pentolite donor which was 2 cm × 2 cm right cylinder; the cell size was smaller in Case 1. Case 3 utilized a composite pentolite donor 2.07 cm long but having stepped diameters of one and two cm; the cell size was quite similar to that of Case 2. Peak (axial) pressure versus distance results from Case 1 were scaled and Compared to experimental data for both the NOL large scale gap test (LSGT) and the NSWC expanded large scale gap test (ELSGT). The comparison was found to be very good for the LSGT but less satisfactory for the ELSGT. Peak (axial) pressure versus distance results from Case 1 were the also compared to Case 2, a coarser zoned model similar to Case 1, and Case 3. This comparison showed that the composite donor produced peak (axial) pressures similar to those from the LSGT model. Normalized peak pressure versus radial distance and shock profiles were compared for the three cases and found to be quite similar. Additional normalized peak pressure versus radial distance and normalized pressure versus time information from Case 1 is plotted to show how the pentolite/PMMA rarefaction affects both the axial and radial pressure‐time histories.
Gun Propulsion Concepts. Part II: Solid and Liquid Propellants
Authors: Maag H.‐J. , Klingenberg Günter
Published: May 2005

The present paper deals with both the conventional solid propellant and modern liquid propellant gun concepts. Solid propellant guns, known since the 14th century, are still being investigated, although this concept represents a relative mature technology. Thus any progress is predominantly a refinement of existing techniques. Comparatively, liquid propellant gun research and development address a rather new technique and invoke some improvements over conventional solid propellant systems. Especially, automatic system are easier to design, artillery zoning is more easily achieved, cartridge disposal is avoided, and high‐energetic liquid propellants or special system designs offer higher performance. Therefore, the liquid propellant gun technology seems to be a near‐term technology that, complementary to solid propellant gun concepts, might play a role in future armament.
Analysis of 3‐Nitro‐1,2,4‐Triazole‐5‐One (NTO) in Explosive Mixtures by capillary electrophoresis
Authors: Oehrle Stuart A.
Published: May 2005

Recently a new explosive, 3‐Nitro‐1,2,4‐triazole‐5‐one (NTO) has attracted interest as possible replacements for or inclusion in various military propellants and explosives. Analysis of NTO compounds as well as 14 other nitramine and nitroaromatic explosives could be accomplished by capillary electrophoresis using a technique known as MECC, micellar electrokinetic capillary chromatography. A borate/boric acid buffer with sodium dodecylsulfate (SDS) was used in conjunction with direct UV detection at 185 nm.
Thermal Decomposition of Energetic Materials 69. Analysis of the kinetics of nitrocellulose at 50 °C–500 °C
Authors: Brill T. B. , Gongwer P. E.
Published: May 2005

Kinetic constants for decomposition of nitrocellulose in the 50 °C to 500°C range are analyzed. At T < 100°C, three processes (depolymerization, peroxide formation, and hydrolysis) are consistent with the reported kinetics. For T = 100°C–200°C, 28 of 30 previously reported kinetic measurements can be organized clearly into two categories by the use of the kinetic compensation effect. These two groups fit the first‐order and autocatalytic processes. Conflicting interpretations are reconciled by this approach. At T > 200°C, the kinetics are consistent with the existence of the first‐order step and desorption of the products as two parallel processes which, together, control the rate. Time‐to‐exotherm and mass burning rate kinetics are compared as temperature‐dependent reaction‐desorption events.
Thermal Degradation of the Binder in GAP‐Based Propellants
Authors: Perreault François , Benchabane Mahmed
Published: May 2005

The long‐term stability of the binder in GAP‐based propellants is investigated in this study. Thermal degradation of the polymer network, being related to the extractable proportion of GAP, is quantified by means of Fourier transform infrared (FTIR) spectroscopy while the degradation products are analysed by size exclusion chromatography (SEC). Our results concerning the aging of four different formulations at 80°C demonstrate the necessity to add a stabilizer like diphenylamine (DPA) to the propellants. Other additives like MgO and TEPANOL are also shown to have a significative stabilizing effect.
Separation of NTO Related 1,2,4‐Triazole‐3‐One Derivatives by a high performance liquid chromatography and capillary electrophoresis
Authors: Le Campion L. , Adeline M. T. , Ouazzani J.
Published: May 2005

This report describes a direct, rapid and sensitive method for separating and quantifying 5‐nitro‐1,2,4‐triazole‐3‐one 1 (NTO) and 5‐amino‐1,2,4‐triazole‐3‐one 2. Analyses were performed on water and on soil containing compounds 1 and/or 2, using reversed phase HPLC columns. A mixture of compounds 1, 2, Urazole 3 and 1,2,4‐triazole‐3‐one 4 was well separated by HPLC on a Hypercarb column packed with porous graphitic carbon, or by capillary electrophoresis. Both methods could be used to detect such compounds in the environment and monitor their biological and chemical degradation.
Modelisation of combustion equilibria with Monte‐Carlo numerical method
Authors: Brunet L. , Forichon‐Chaumet N. , Lombard J. M. , Espagnacq A.
Published: May 2005

The computation of complex combustions is made classically by using an iterative Newton‐Raphson method, applied to the resolution of a system of equations under constraint by the method of Lagrange multipliers. In many mineral combustions, there are products of reaction that present the same formula but belong to different phases (solids, liquids or gaseous). In these cases, the classic method ends frequently in singular matrix. Indeed, combustion equations can present in these cases, several equal or very close solutions, which induce a numerical fork phenomenon (“stiff” problems) and a chaotic algorithm behaviour. The method presented uses a Monte‐Carlo random algorithm: the Method of Random mass Statements. It presents the advantage of converging in numerically stiff cases. It furthermore provides results equal to the classic method for non‐stiff problems.
HPLC optimization of the separation of explosives and propellant components with an octadecyl phase by computer simulation
Authors: Kaiser Manfred
Published: May 2005

High performance liquid chromatography (HPLC) is used in a large extent for environmental analysis. In this field many components have to be determined at the same time, but it is difficult to find the optimum separation conditions. Therefore, retention times of explosives and propellant components were determined at different solvent compositions of methanol/water and different temperatures on a column with an octadecyl phase. From the data constants were calculated for solvent and temperature dependence. With the determined data different column conditions were simulated by computer and the separation was optimized. The optimal separation was verified experimentally and compared with the calculated values. The deviation from calculated and experimental retention times lies as a rule below 2% and has a maximum of approximately 3.3%. Thus, separation of substance mixtures can be optimized by determination of column constants for temperature and solvent dependence.
Numerical Modeling of Underwater Explosion Properties for an aluminized explosive
Authors: Lee Jaimin , Kuk Jeong‐Hyun , Cho Yong‐Soo , Song So‐young , Lee Jun‐Wung
Published: May 2005

Underwater explosion properties of an aluminized explosive, DXD‐03, were numerically modeled by two burn techniques; a programmed‐burn technique and a rate equation calibrated from two‐dimensional steady‐state detonation experiments based on the detonation shock dynamics. The modeling by using the programmed‐burn technique did not reproduce experimental data well; 12% to 34% error in peak pressure and 20% error in bubble period. The modeling by using the rate equation reproduced the experimental observations very well. Although there was some difference in peak pressure, the shock profile agreed very well with experimental observation. The calculated bubble period agreed with the experimental data within 1%. This result demonstrates that the underwater explosion properties for aluminized explosives can be calculated only when the slow energy release of aluminium is modeled properly.
Energetics of charge–charge interactions in proteins
Authors: Gilson Michael K. , Honig Barry H.
Published: May 2005

Electrostatic interactions between pairs of atoms in proteins are calculated with a model based on the linearized Poisson‐Boltzmann equation. The equation is solved accurately by a method that takes into account the detailed shape of the protein. This paper presents applications to several systems. Experimental data for the interaction of ionized residues with an active site histidine in subtilisin BPN' allow the model to be tested, using various assumptions for the electrical properties of the protein and solvent. The electrostatic stabilization of the active site thiolate or rhodanese is analyzed, with attention to the influence of α‐helices. Finally, relationships between electrostatic potential and charge‐charge distance are reported for large and small globular proteins. The above results are compared with those of simpler electrostatic models, including Coulomb's law with both a distance‐dependent dielectric constant (ϵ = R) and a fixed dielectric constant (ϵ = 2), and Tanford‐Kirkwood theory. The primary conclusions are as follows: (1) The Poisson‐Boltzmann model agrees with the subtilisin data over a range of ionic strengths; (2) two α‐helices generate a large potential in the active site of rhodanese; (3) ϵ = R overestimates weak electrostatic interactions but yields relatively good results for strong ones; (4) Tanford‐Kirkwood theory is a useful approximation to detailed solutions of the linearized Poisson‐Boltzmann equation in globular proteins; and (5) the modified Tanford‐Kirkwood theory overscreens the measured electrostatic interactions in subtilisin.
Protein stability and electrostatic interactions between solvent exposed charged side chains
Authors: Akke Mikael , Forsén Sture
Published: May 2005

To investigate the contribution to protein stability of electrostatic interactions between charged surface residues, we have studied the effect of substituting three negatively charged solvent exposed residues with their side‐chain amide analogs in bovine calbindin D9k—a small (Mr 8,500) globular protein of the calmodulin superfamily. The free energy of urea‐induced unfolding for the wildtype and seven mutant proteins has been measured. The mutant proteins have increased stability towards unfolding relative to the wildtype. The experimental results correlate reasonably well with theoretically calculated relative free energies of unfolding and show that electrostatic interactions between charges on the surface of a protein can have significant effects on protein stability.
Crystallographic refinement of human serum retinol binding protein at 2Å resolution
Authors: Cowan Sandra W. , Newcomer Marcia E. , Jones T. Alwyn
Published: May 2005

Human serum retinol binding protein (RBP) in complex with retinol has been crystallographically refined to an R‐factor of 18.1% with 2Å resolution data. The protein topology results in an anti‐parallel β‐barrel that encapsulates the retinol ligand. A detailed description of the protein and the binding site is provided. Our structural work has helped to define a family of proteins, many of which are carrier proteins for smaller ligand molecules. We describe the structural basis for the conservation of sequence within the family.
Revised 2.3 Å structure of porcine pepsin: Evidence for a flexible subdomain
Authors: Abad‐Zapatero Cele , Rydel Timothy J. , Erickson John
Published: May 2005

A revised three‐dimensional crystal structure of ethanol‐inhibited porcine pepsin refined to an R‐factor of 0.171 at 2.3 Å resolution is presented and compared to the refined structures of the fungal aspartic proteinases: penicillopepsin, rhizopuspepsin, and endothiapepsin. Pepsin is composed of two nearly equal N and C domains related by an intra dyad. The overall polypeptide fold and active site structures are homologous for pepsin and the fungal enzymes. The weak inhibition of pepsin by ethanol can be explained by the presence of one or more ethanol molecules, in the vicinity of the active site carboxylates, which slightly alter the hydrogen‐bonding network and which may compete with substrate binding in the active site. Structural superposition analysis showed that the N domains aligned better than the C‐domains for pepsin and the fungal aspartic proteinases: 107–140 Cα pairs aligned to 0.72–0.85 Å rms for the N domains; 64–95 Cα pairs aligned to 0.78–1.03 Å rms for the C domains. The major structural difference between pepsin and the fungal enzymes concerns a newly described subdomain whose conformation varies markedly among these enzyme structures. The subdomain in pepsin comprises nearly 100 residues and is composed of two contiguous segments within the C domain (residues 192–212 and 223–299). The subdomain is connected, or “hinged,” to a mixed β‐sheet that forms one of the structurally invariant, active site ψ‐loops. Relative subdomain displacements as large as a 21.0° rotation and a 5.9 Å translation were observed among the different enzymes. There is some suggestion in pepsin that the subdomain may be flexible and perhaps plays a structural role in mediating substrate binding, determining the substrate specificity, or in the activation of the zymogen.
Helix packing of leucine‐rich peptides: A parallel leucine ladder in the structure of Boc‐Aib‐Leu‐Aib‐Aib‐Leu‐Leu‐Leu‐Aib‐Leu‐Aib‐OMe
Authors: Karle Isabella L. , Flippen‐Anderson Judith L. , Sukumar M. , Balaram P.
Published: May 2005

The packing of peptide helices in crystals of the leucine‐rich decapeptide Boc‐Aib‐Leu‐Aib‐Aib‐Leu‐Leu‐Leu‐Aib‐Leu‐Aib‐OMe provides an example of ladder‐like leucylleucyl interactions between neighboring molecules. The peptide molecule forms a helix with five 5→1 hydrogen bonds and two 4→1 hydrogen bonds near the C terminus. Three head‐to‐tail NH ċ O = C hydrogen bonds between helices form continuous columns of helices in the crystal. The helicial columns associate in an antiparallel fashion, except for the association of Leu ċ Leu side chains, which occurs along the diagonal of the cell where the peptide helices are parallel. The peptide, with formula C56H102N10O13, crystallizes in space group P212121 with Z = 4 and cell parameters a = 16.774(3) Å, b = 20.032(3) Å and c = 20.117(3) Å; overall agreement factor R = 10.7% for 2014 data with |Fobs| < 3σ(F); resolution 1.0 Å.
Protease pro region required for folding is a potent inhibitor of the mature enzyme
Authors: Baker David , Silen Joy L. , Agard David A.
Published: May 2005

α‐Lytic protease, an extracellular bacterial serine protease, is synthesized with a large pro region that is required in vivo for the proper folding of the protease domain. To allow detailed mechanistic study, we have reconstituted pro region‐dependent folding in vitro. The pro region promotes folding of the protease domain in the absence of other protein factors or exogenous energy sources. Surprisingly, we find that the pro region is a high affinity inhibitor of the mature protease. The pro region also inhibits the closely related Streptomyces griseus protease B, but not the more distantly related, yet structurally similar protease, elastase. Based on these data, we suggest a mechanism in which pro region binding reduces the free energy of a late folding transition state having native‐like structure.
Use of conditional probabilities for determining relationships between amino acid sequence and protein secondary structure
Authors: Arnold Gregory E. , Dunker A. Keith , Johns Susan J. , Douthart Richard J.
Published: May 2005

The conditional probability, P(σ|x), is a statement of the probability that the value of σ will be found given the prior information that a value of x has been observed. Here σ represents any one of the secondary structure types, α, β, τ, and ρ for helix, sheet, turn, and random, respectively, and x represents a sequence attribute, including, but not limited to: (1) hydropathy; (2) hydrophobic moments assuming helix and sheet; (3) Richardson and Richardson helical N‐cap and C‐cap values; (4) Chou–Fasman conformational parameters for helix, Pα, for sheet, Pβ, and for turn, Pτ; and (5) Garnier, Osguthorpe, and Robson (GOR) information values for helix, Iα, for sheet, Iβ, for turn, I,τ, and for random structure, Iρ.

Plots of P (σ|x) vs. x are demonstrated to provide information about the correlation between structure and attribute, σ and x. The separations between different P (σ|x) vs. x curves indicate the capacity of a given attribute to discriminate between different secondary structural types and permit comparison of different attributes. P (α|x), P (β|x), P (τ|x) and P (ρ|x) vs. x plots show that the most useful attributes for discriminating helix are, in order: hydrophobic moment assuming helix > Pα » N‐cap > C‐cap ≈ Iα ≈ Iτ. The information value for turns, Iτ, was found to discriminate helix better than turns. Discrimination for sheet was found to be in the following order: Iβ » Pβ ≈ hydropathy > Iρ ≈ hydrophobic moment assuming sheet.

Three attributes, at their low values, were found to give significant discrimination for the absence of helix: Iα ≈ Pα ≈ hydrophobic moment assuming helix. Also, three other attributes were found to indicate the absence of sheet: Pβ » Iτ ≈ hydropathy. Indications of the absence of σ could be as useful for some applications as the indication of the presence of σ.
Structures of the “open” and “closed” state of trypanosomal triosephosphate isomerase, as observed in a new crystal form: Implications for the reaction mechanism
Authors: Noble Martin E. M. , Zeelen Johan Ph. , Wierenga Rik K.
Published: May 2005

The structure of trypanosomal triosephosphate isomerase (TIM)has been solved at a resolution of 2.1Å in a new crystal form grown at pH 8.8 from PEG6000. In this new crystal form (space group C2, cell dimensions 94.8 Å, 48.3 Å, 131.0 Å, 90.0°, 100.3°, 90.0°), TIM is present in a ligand‐free state. The asymmetric unit consists of two TIM subunits. Each of these subunits is part of a dimer which is sitting on a crystallographic twofold axis, such that the crystal packing is formed from two TIM dimers in two distinct environments. The two constituent monomers of a given dimer are, therefore, crystallographically equivalent. In the ligand‐free state of TIM in this crystal form, the two types of dimer are very similar in structure, with the flexible loops in the “Open” conformation. For one dimer (termed molecule‐1), the flexible loop (loop‐6) is involved in crystal contacts. Crystals of this type have been used in soaking experiments with 0.4 M ammonium sulphate (studied at 2.4 Å resolution), and with 40 μM phosphoglycolohydroxamate (studied at 2.5 Å resolution). It is found that transfer to 0.4 M ammonuum sulphate (equal to 80 times the Ki of sulphate for TIM), gives rise to significant sulphate binding at the active site of one dimer (termed molecule‐2), and less significant binding at the active site of the other. In neither dimer does sulphate induce a “closed” conformation. In a mother liquor containing 40 μM phosphoglycolohydroxamate (equal to 10 times the Ki of phosphoglycolohydroxamate for TIM), an inhibitor molecule binds at the active site of only that dimer of which the flexible loop is free from crystal contacts (molecule‐2). In this dimer, it induces a closed conformation. These three structures are compared and discussed with respect to the mode of binding of ligand in the active site as well as with respect to the conformational changes resulting from ligand binding. © 1993 Wiley‐Liss, Inc.
Dynamic properties of some β‐chain mutant hemoglobins
Authors: Militello V. , Cupane A. , Leone M. , Brinigar W. S. , Lu A.‐L. , Fronticelli C.
Published: May 2005

The thermal behavior of the Soret band relative to the carbonmonoxy derivatives of some β‐chain mutant hemoglobins is studied in the temperature range 300–10 K and compared to that of wild‐type carbonmonoxy hemoglobin. The band profile at various temperatures is modeled as a Voigt function that accounts for homogeneous broadening and for the coupling with high‐ and low‐frequency vibrational modes, while inhomogeneous broadening is taken into account with a gaussian distribution of purely electronic transition frequencies. The various contributions to the overall bandwidth are singled out With this analysis and their temperature dependence, in turn, gives information on structural and dynamic properties of the system studied. In the wildtype and mutant hemoglobins, the values of homogeneous bandwidth and of the coupling constants to high‐frequency vibrational modes are not modified with respect to natural human hemoglobin, thus indicating that the local electronic and vibrational properties of the heme–CO complex are not altered by the recombinant procedures. On the contrary, differences in the protein dynamic behavior are observed. The most relevant are those relative to the “polar isosteric” βVal‐67(Ell) →Thr substitution, localized in the heme pocket, which results in decreased coupling with low‐frequency modes and increased anharmonic motions. Mutations involving residue βLys‐144(HC1) at the C‐terminal and residue βCys‐112(G14) at the α1β1 interface have a smaller effect consisting in an increased coupling with low‐frequency modes. Mutations at the β‐N‐terminal and at the α1β2 interface have no effect on the dynamic properties of the heme pocket. © 1995 Wiley‐Liss, Inc.
Crystallization and preliminary X‐ray diffraction studies of leishmanolysin, the major surface metalloproteinase from Leishmania major
Authors: Schlagenhauf Edith , Etges Robert , Metcalf Peter
Published: May 2005

The membrane‐bound GPI‐anchored zinc metalloproteinase leishmanolysin purified from Leishmania major promastigotes has been crystallized in its mature form. Two crystal forms of leishmanolysin have been grown by the vapor diffusion method using 2‐methyl‐2,4‐pentanediol as the precipitant. Macroseeding techniques were employed to produce large single crystals. Protein microhet‐erogeneity in molecular size and charge was incorporated into both crystal forms. The tetragonal crystal form belongs to the space group P41212 or the enantiomorph P43212, has unit cell parameters of a = b = 63.6 Å, c = 251.4 Å, and contains one molecule per asymmetric unit. The second crystal form is monoclinic, space group C2, with unit cell dimensions a = 107.2 Å, b = 90.6 Å, c = 70.6 Å, β = 110.6°, and also contains one molecule per asymmetric unit. Both crystal forms diffract X‐rays beyond 2.6 Å resolution and are suitable for X‐ray analysis. Native diffraction data sets have been collected and the structure determination of leishmanolysin using a combination of the isomorphous replacement and the molecular replacement methods is in progress. © 1995 Wiley‐Liss, Inc.
Crystallization and preliminary X‐ray diffraction studies of the cartilage link protein from bovine trachea
Authors: Jedrzejas Marek J. , Baker John R. , Luo Ming
Published: May 2005

Cartilage extracellular matrix link protein, having molecular mass of approximately 40 kDa, is a metalloprotein that binds divalent cations and is only soluble in low ionic strength solutions. The link protein was purified from bovine trachea and has been crystallized by a vapor diffusion method using PEG 3350 as precipitant. The crystal symmetry is P1, and the unit cell dimensions are a = 43.55, b = 53.11, c = 60.10 Å, α = 90.44, β = 106.21, γ = 101.51°. The VM of 1.8 Å3/Da is consistent with the presence of two molecules of the link protein in the asymmetric unit. The crystals diffract X‐rays from a synchrotron source to 1.7 Å resolution. © 1995 Wiley‐Liss, Inc.
Massive cluster impact mass spectrometry: A new desorption method for the analysis of large biomolecules
Authors: Mahoney J. F. , Perel J. , Ruatta S. A. , Martino P. A. , Husain S. , Cook Kelsey , Lee T. D.
Published: May 2005

A new ion desorption method is described that utilizes a primary beam of massive, multiply charged cluster ions to generate secondary ions of peptides in a glycerol matrix. The massive cluster ion beam is generated via electrohydrodynamic emission using a 1.5 M solution of ammonium acetate in 30% aqueous glycerol. Negaitve ion spectra of peptides obtained using this technique show greatly decreased relative intensities for fragment ions and ‘chemical noise’ background when compared to spectra obtained using a xenon atom primary beam. The near absence of fragmets derived from radiation damage to the sample solution is attributed to the impact of primary particles with energies less than 1 eV/nucleon.
A mass spectrometric investigation of mono‐, di‐ and trimethylenebis (disphenylphosphine)‐ Pt(II)‐cis‐dichloro and ‐dicyano derivatives
Authors: Vianello Sebastiano , Bonivento Massimiliano , Cattalini Lucio , Curcuruto Ornella , Traldi Pietro , Chapman J. R.
Published: May 2005

The mass spectrometric behaviour of mono‐, di‐ and trimethylenebis(diphenylphosphine)‐Pt(II)‐cis‐dichloro and ‐dicyano drivatives has been studied with the aid of two different ionization techniques (electron ionization and fast‐atom bombardment) and metastable ion studies, with the aim of finding the most suitable mass spectrometric technique for determining the real monomeric or dimeric structure of such compounds. Electron ionization mass spectrometry led to the best results in terms of molecular ion identification and production of fragment ions well‐related to the original structure. On the contrary, fast‐atom bombardment led to the formation of dimeric species for Pt{1,2‐bis(diphenylphosphino)methane}Cl2 and Pt{1,2‐bis(diphenylphosphino)methane}(CN)2 due to the high reactivity of the monomeric molecules in the condensed phase.
Methane chemical ionization of pesticides by ion‐trap technology: Spectral characteristics and data precision
Authors: Cairns Thomas , Chiu Kin. S. , Siegmund Emil
Published: May 2005

Examination of the methane chemical ionization (CI) spectra produced in an ion trap under automatic reaction control has revealed a strong concentration dependence phenomenon even at trace levels (ppm). The spectra produced during the elution profile of various pesticides via capillary gas‐chromatographic introduction have indicated a large percentage of an electron ionization (EI) spectral component superimposed on the CI spectrum. This duplicity of spectral character can be an important asset for confirmation of presence and it does not present a problem of obtaining acceptable precision and accuracy on quantification of pesticide residues. Identification of residues using the standard spectral library databased derived from other sources might require careful scrutiny before acceptance.