Clear evidence for element partitioning effects in a Ti-6Al-4V alloy by the first-principles phase field method

Ti-6 wt% Al-4 wt% V (Ti64) is an α + β titanium alloy, in which the alloying components strongly affect the mechanical properties. In this report, element partitioning effects in Ti64 are investigated by using the first-principles phase field (FPPF) method, which has recently been proposed by our group. In the FPPF method, the local free energy is calculated using a cluster expansion method in combination with density functional theory and the temperature effect is incorporated using potential renormalization theory. We have succeeded in identifying enrichment of Al (V) in the α (β) phase, i.e., the clear evidence for the element partitioning effects of Al and V, without using any thermodynamical parameter. The transformation of the β phase and the α phase in microstructure is investigated by varying the V and Al concentrations by a small amount. Our results are in excellent agreement with the recent experimental results, showing the validity of the FPPF method for ternary alloys.

MAS NMR Investigation of Molecular Order in an Ionic Liquid Crystal

The structure and molecular order in the thermotropic ionic liquid crystal (ILC), [choline][geranate(H)octanoate], an analogue of Choline And GEranate (CAGE), which has potential for use as a broad-spectrum antimicrobial and transdermal and oral delivery agent, were investigated by magic-angle spinning (MAS) nuclear magnetic resonance (NMR), polarizing optical microscopy, small-angle X-ray scattering (SAXS), and mass spectrometry. Mass spectrometry and the ¹H NMR chemical shift reveal that CAGE-oct is a dynamic system, with metathesis (the exchange of interacting ions) and hydrogen exchange occurring between hydrogen-bonded/ionic complexes such as [(choline)(geranate)(H)(octanoate)], [(choline)(octanoate)₂(H)], and [(choline)(geranate)₂(H)]. These clusters, which are shown by mass spectrometry to be significantly more stable than expected for typical electrostatic ion clusters, involve hydrogen bonding between the carboxylic acid, carboxylate, and hydroxyl groups, with rapid hydrogen bond breaking and re-formation observed to average the ¹H chemical shifts. The formation of a partial bilayer liquid crystal (LC) phase was identified by SAXS and polarizing optical microscopy at temperatures below ∼293 K. The occurrence of this transition close to room temperature could be utilized as a potential temperature-induced "switch" of the anisotropic properties for particular applications. The presence of an isotropic component of approximately 23% was observed to coexist with the LC phase, as detected by polarizing optical microscopy and quantified by both ¹H-¹³C dipolar-chemical shift correlation (DIPSHIFT) and ¹H double-quantum (DQ) MAS NMR experiments. At temperatures above the LC-to-isotropic transition, intermediate-range order (clustering of polar and nonpolar domains), a feature of many ILs, persists. Site-specific order parameters for the LC phase of CAGE-oct were obtained from the MAS NMR measurement of the partially averaged ¹³C-¹H dipolar couplings (D_CH) by cross-polarization (CP) build-up curves and DIPSHIFT experiments, and ¹H-¹H dipolar couplings (D_HH) by double-quantum (DQ) build-up curves. The corresponding order parameters, S_CH and S_HH, are in the range 0-0.2 and are lower compared to those for smectic (i.e., layered) phases of conventional nonionic liquid crystals, resembling those of lamellar phases formed by lyotropic surfactant-solvent systems.

Local Structural Effects Due to Micronization and Amorphization on an HIV Treatment Active Pharmaceutical Ingredient

Processing procedures for inducing domain size reduction and/or amorphous phase generation can be crucial for enhancing the bioavailability of active pharmaceutical ingredients (APIs). It is important to quantify these reduced coherence phases and to detect and characterize associated structural changes, to ensure that no deleterious effects on safety, function, or stability occur. Here, X-ray powder diffraction (XRPD), total scattering pair distribution function (TSPDF) analysis, and solid-state nuclear magnetic resonance spectroscopy (SSNMR) have been performed on samples of GSK2838232B, an investigational drug for the treatment of human immunodeficiency virus (HIV). Preparations were obtained through different mechanical treatments resulting in varying extents of domain size reduction and amorphous phase generation. Completely amorphous formulations could be prepared by milling and microfluidic injection processes. Microfluidic injection was shown to result in a different local structure due to dispersion with dichloromethane (DCM). Implications of combined TSPDF and SSNMR studies to characterize molecular compounds are also discussed, in particular, the possibility to obtain a thorough structural understanding of disordered samples from different processes.

Revealing Intermolecular Hydrogen Bonding Structure and Dynamics in a Deep Eutectic Pharmaceutical by Magic-Angle Spinning NMR Spectroscopy

Liquid forms of pharmaceuticals (ionic liquids and deep eutectic solvents) offer a number of potential advantages over solid-state drugs; a key question is the role of intermolecular hydrogen bonding interactions in enabling membrane transport. Characterization is challenging since high sample viscosities, typical of liquid pharmaceutical formulations, hamper the use of conventional solution NMR at ambient temperature. Here, we report the application of magic-angle spinning (MAS) NMR spectroscopy to the deep eutectic pharmaceutical, lidocaine ibuprofen. Using variable temperature MAS NMR, the neat system, at a fixed molar ratio, can be studied over a wide range of temperatures, characterized by changing mobility, using a single experimental setup. Specific intermolecular hydrogen bonding interactions are identified by two-dimensional ¹H-¹H NOESY and ROESY MAS NMR experiments. Hydrogen-bonding dynamics are quantitatively determined by following the chemical exchange process between the labile protons by means of line-width analysis of variable temperature ¹H MAS NMR spectra.

Progress towards rabies control and elimination in Vietnam

Rabies is a fatal viral disease that causes an estimated 59,000 human deaths each year. The majority of these deaths occur in developing countries in Asia. Canine rabies is endemic to Vietnam, which is, however, moving towards the disease's elimination. Many countries, such as Vietnam, have invested tremendous resources in controlling rabies, highlighting the goal of regional and global elimination of this neglected disease. In Vietnam, rabies is recognised as one of five high-priority, zoonotic diseases by the Ministry of Health and the Ministry of Agriculture and Rural Development. Investment by the government and by international partners for rabies prevention and control has played a substantial role in reducing human rabies deaths from 404 cases in 1992 to 74 cases in 2017. The catalyst for this effort was the Prime Minister's creation of the National Rabies Program in 1996, which led to increased support and resources for rabies prevention and control. Interventions carried out since then include the expansion of post-exposure prophylaxis centres throughout the country, the introduction or revision of key legislation and guidelines, and improved multisectoral One Health collaboration. In addition, support from international partners, such as the World Organisation for Animal Health (OIE), the World Health Organization (WHO), the Food and Agriculture Organization of the United Nations (FAO), and the Centers for Disease Control and Prevention (CDC), has helped to increase awareness, manage dog populations more effectively, and improve Vietnam's surveillance and diagnostic capabilities. To pursue the goal of eliminating dog-mediated rabies in Vietnam, political commitment is crucial. Resources must be made available to enforce the regulations and guidelines that will enable Vietnam to achieve greater canine rabies vaccination coverage. In this paper, the authors provide an overview of the animal and human health systems in Vietnam, as well as past, current and future directions of rabies prevention and control.

Prospective observational study comparing burn surgeons' estimations of wound healing after skin grafting to photo-assisted methods

INTRODUCTION

Appropriate graft healing after split-thickness skin graft and early recognition of complications (graft loss) are critical to burn patient management. Larger mesh ratio expansions and Meek micrografting may pose a greater challenge in estimating the percentage of wound healing. This study looks at the reliability of photograph assessments and the concordance of bedside evaluation to photograph assessments of wound healing after skin grafting.

METHODS

Three assessment methods for percentage of wound healing after skin Grafting were assessed: (1) clinicians' bedside rating, (2) clinician assessment of high-definition photographs, and (3) digital image analysis through color subtraction using Adobe Photoshop. We compared each method using a mixed-effects model on absolute agreement using intra-class correlation (ICC) and Bland Altman (BA) plots.

RESULTS

Fourteen burn patients were enrolled with 38 grafted wounds (100 sites). Bedside assessments had a mean ICC of 0.64 (compared to digital image analysis) and 0.69 (compared to photo assessment), with a wide range on BA-plots. Inter-rater reliability of photo assessment was excellent (0.96) among six clinicians. Repeated photo-assisted assessments had good intra-rater reliability (ICC: photo assessment: 0.88; digital analysis: 0.97).

CONCLUSIONS

Bedside wound healing assessments show variability; photograph documentation of sequential wound progression could supplement active clinical management or studies for more reliable assessments.

Managing emerging mutagenicity risks: Late stage mutagenic impurity control within the atovaquone second generation synthesis

The mutagenic-impurity control strategy for a second generation manufacturing route to the non-mutagenic antipneumocystic agent atovaquone (2-((1R,4R)-4-(4-chlorophenyl)cyclohexyl)-3-hydroxynaphthalene-1,4-dione) 1 is described. Preliminary assessment highlighted multiple materials of concern which were largely discharged either through returning a negative bacterial mutagenicity assay or through confidence that the impurity would be purged during the downstream processing from when it was first introduced. Additional genotoxicity testing highlighted two materials of concern where initial assessment suggested that testing for these impurities at trace levels within the drug substance would be required. Following a thorough review of process purging detail, spiking and purging experimentation, and an understanding of the process parameters to which they were exposed an ICH M7 Option 4 approach could be justified for their control. The development of two 1H NMR spectroscopy methods for measurement of these impurities is also described as well as a proposed summary table for describing the underlying rationale for ICH M7 control rationales to regulators. This manuscript demonstrates that process purging of potential mutagenic impurities can be realised even when they are introduced in the later stages of a process and highlights the importance of scientific understanding rather than relying on a stage-counting approach.

Identifying guanosine self assembly at natural isotopic abundance by high-resolution 1H and 13C solid-state NMR spectroscopy

By means of the (1)H chemical shifts and the proton-proton proximities as identified in (1)H double-quantum (DQ) combined rotation and multiple-pulse spectroscopy (CRAMPS) solid-state NMR correlation spectra, ribbon-like and quartet-like self-assembly can be identified for guanosine derivatives without isotopic labeling for which it was not possible to obtain single crystals suitable for diffraction. Specifically, characteristic spectral fingerprints are observed for dG(C10)(2) and dG(C3)(2) derivatives, for which quartet-like and ribbon-like self-assembly has been unambiguously identified by (15)N refocused INADEQUATE spectra in a previous study of (15)N-labeled derivatives (Pham, T. N.; et al. J. Am. Chem. Soc.2005, 127, 16018). The NH (1)H chemical shift is observed to be higher (13-15 ppm) for ribbon-like self-assembly as compared to 10-11 ppm for a quartet-like arrangement, corresponding to a change from NH···N to NH···O intermolecular hydrogen bonding. The order of the two NH(2)(1)H chemical shifts is also inverted, with the NH(2) proton closest in space to the NH proton having a higher or lower (1)H chemical shift than that of the other NH(2) proton for ribbon-like as opposed to quartet-like self-assembly. For the dG(C3)(2) derivative for which a single-crystal diffraction structure is available, the distinct resonances and DQ peaks are assigned by means of gauge-including projector-augmented wave (GIPAW) chemical shift calculations. In addition, (14)N-(1)H correlation spectra obtained at 850 MHz under fast (60 kHz) magic-angle spinning (MAS) confirm the assignment of the NH and NH(2) chemical shifts for the dG(C3)(2) derivative and allow longer range through-space N···H proximities to be identified, notably to the N7 nitrogens on the opposite hydrogen-bonding face.

Analysis of amorphous solid dispersions using 2D solid-state NMR and (1)H T(1) relaxation measurements

Solid-state NMR (SSNMR) can provide detailed structural information about amorphous solid dispersions of pharmaceutical small molecules. In this study, the ability of SSNMR experiments based on dipolar correlation, spin diffusion, and relaxation measurements to characterize the structure of solid dispersions is explored. Observation of spin diffusion effects using the 2D (1)H-(13)C cross-polarization heteronuclear correlation (CP-HETCOR) experiment is shown to be a useful probe of association between the amorphous drug and polymer that is capable of directly proving glass solution formation. Dispersions of acetaminophen and indomethacin in different polymers are examined using this approach, as well as (1)H double-quantum correlation experiments to probe additional structural features. (1)H-(19)F CP-HETCOR serves a similar role for fluorinated drug molecules such as diflunisal in dispersions, providing a rapid means to prove the formation of a glass solution. Phase separation is detected using (13)C, (19)F, and (23)Na-detected (1)H T(1) experiments in crystalline and amorphous solid dispersions that contain small domains. (1)H T(1) measurements of amorphous nanosuspensions of trehalose and dextran illustrate the ability of SSNMR to detect domain size effects in dispersions that are not glass solutions via spin diffusion effects. Two previously unreported amorphous solid dispersions involving up to three components and containing voriconazole and telithromycin are analyzed using these experiments to demonstrate the general applicability of the approach.

Complete (1)H resonance assignment of beta-maltose from (1)H-(1)H DQ-SQ CRAMPS and (1)H (DQ-DUMBO)-(13)C SQ refocused INEPT 2D solid-state NMR spectra and first principles GIPAW calculations

A disaccharide is a challenging case for high-resolution (1)H solid-state NMR because of the 24 distinct protons (14 aliphatic and 10 OH) having (1)H chemical shifts that all fall within a narrow range of approximately 3 to 7 ppm. High-resolution (1)H (500 MHz) double-quantum (DQ) combined rotation and multiple pulse sequence (CRAMPS) solid-state NMR spectra of beta-maltose monohydrate are presented. (1)H-(1)H DQ-SQ CRAMPS spectra are presented together with (1)H (DQ)-(13)C correlation spectra obtained with a new pulse sequence that correlates a high-resolution (1)H DQ dimension with a (13)C single quantum (SQ) dimension using the refocused INEPT pulse-sequence element to transfer magnetization via one-bond (13)C-(1)H J couplings. Compared to the observation of only a single broad peak in a (1)H DQ spectrum recorded at 30 kHz magic-angle spinning (MAS), the use of DUMBO (1)H homonuclear decoupling in the (1)H DQ CRAMPS experiment allows the resolution of distinct DQ correlation peaks which, in combination with first-principles chemical shift calculations based on the GIPAW (Gauge Including Projector Augmented Waves) plane-wave pseudopotential approach, enables the assignment of the (1)H resonances to the 24 distinct protons. We believe this to be the first experimental solid-state NMR determination of the hydroxyl OH (1)H chemical shifts for a simple sugar. Variable-temperature (1)H-(1)H DQ CRAMPS spectra reveal small increases in the (1)H chemical shifts of the OH resonances upon decreasing the temperature from 348 K to 248 K.

The refocused INADEQUATE MAS NMR experiment in multiple spin-systems: interpreting observed correlation peaks and optimising lineshapes

The robustness of the refocused INADEQUATE MAS NMR pulse sequence for probing through-bond connectivities has been demonstrated in a large range of solid-state applications. This pulse sequence nevertheless suffers from artifacts when applied to multispin systems, e.g. uniformly labeled (13)C solids, which distort the lineshapes and can potentially result in misleading correlation peaks. In this paper, we present a detailed account that combines product-operator analysis, numerical simulations and experiments of the behavior of a three-spin system during the refocused INADEQUATE pulse sequence. The origin of undesired anti-phase contributions to the spectral lineshapes are described, and we show that they do not interfere with the observation of long-range correlations (e.g. two-bond (13)C-(13)C correlations). The suppression of undesired contributions to the refocused INADEQUATE spectra is shown to require the removal of zero-quantum coherences within a z-filter. A method is proposed to eliminate zero-quantum coherences through dephasing by heteronuclear dipolar couplings, which leads to pure in-phase spectra.

Measurement of1H–1H Residual Dipolar Coupling Constants for Structural Studies of Medium Size Molecules

Residual dipolar coupling constants (RDCs) are being increasingly applied to elucidate the configuration and conformation of small organic molecules, peptides and oligosaccharides. In this paper we describe a set of robust 1D NMR methods for accurate and precise measurement of proton-proton RDCs of small and medium size molecules. The performance of these techniques is not impeded by the presence of overlapping and broad (1)H multiplets that are typically observed for such molecules in weakly aligned media. The use of these techniques provides access to a large pool of proton-proton RDCs opening new avenues for the solution structure elucidation of medium size molecules by NMR. The techniques are illustrated on the determination of the alignment tensor of the reducing monosaccharide ring of cellobiose and the determination of the relative configuration of sodium cholate.

Quantifying hydrogen-bonding strength: the measurement of 2hJNN couplings in self-assembled guanosines by solid-state 15N spin-echo MAS NMR

(2h)J(NN) hydrogen-bond mediated J couplings are measured in the solid state for two synthetic deoxyguanosine derivatives by (15)N MAS NMR spin-echo experiments. The use of rotor-synchronised Hahn-echo pulse train (RS-HEPT) (1)H decoupling, with a duty cycle of 6%, allows spin-echo durations out to 200 ms, hence enabling the accurate determination of J couplings as small as 3.8 Hz. A single-crystal X-ray diffraction structure exists for the shorter alkyl chain derivative dG(C(3))(2): the observation of significantly different (2h)J(NN) couplings, 6.2 +/- 0.4 and 7.4 +/- 0.4 Hz, for the two resolved N7 resonances is to be expected given the NH...N hydrogen-bonding distances of 2.91 and 2.83 A for the two distinct molecules in the asymmetric unit cell. For the longer alkyl chain derivative, dG(C(10))(2), for which there is no single-crystal diffraction structure, a (15)N refocused INADEQUATE spectrum (Pham et al., J. Am. Chem. Soc., 2005, 127, 16018-16019) has demonstrated the presence of N2-H...N7 intermolecular hydrogen-bonds indicative of a quartet-like structure. The (2h)J(NN) hydrogen-bond mediated J coupling of 5.9 +/- 0.2 Hz is at the lower end of the range (5.9-8.2 Hz) of (2h)J(NN) couplings determined from solution-state NMR of guanosine quartets in quadruplex DNA. A full discussion of the determination of error bars on the fitted parameters is given; specifically, error bars determined by a non-linear fitting (using the covariance matrix) or in a Monte-Carlo fashion are found to give effectively identical results.

Identification by15N Refocused INADEQUATE MAS NMR of Intermolecular Hydrogen Bonding that Directs the Self-Assembly of Modified DNA Bases

15N solid-state NMR refocused INADEQUATE spectra of two lipophilic deoxyguanosine derivatives unambiguously identify different intermolecular hydrogen-bonding arrangements that are indicative of either guanine ribbon or quartet self-assembly. The observation of guanine quartet formation in the absence of metal ions is a further example that challenges the accepted dogma that quartet formation requires metal ions.

1H-detected double-J-modulated INEPT-INADEQUATE for simultaneous determination of one-bond and long-range carbon-carbon connectivities and the measurement of all carbon-carbon coupling constants

We describe a new NMR experiment, (1)H-detected double-J-modulated (DJM)-INEPT-INADEQUATE, for tracing out the carbon skeleton of molecules. This experiment allows simultaneous correlation of directly bonded carbon atoms and those separated by multiple bonds, while at the same time also providing the values of all J(CC) coupling constants. This is achieved by replacing both fixed carbon-carbon coupling evolution intervals of the INEPT-INADEQUATE experiment by variable time intervals, which are incremented in concert with the DQ evolution period (t(1)). We show that the analysis of the fine structure of cross-peaks in DJM-INEPT-INADEQUATE spectra leads to accurate values of coupling constants and give guidelines for the proper usage of the method. The proposed experiment is two times less sensitive that the original INEPT-INADEQUATE experiment. We show that, using a 600-MHz cryoprobe and 20 mg of a monosaccharide, spectra that are suitable for the analysis of coupling constants as small as 2 Hz can be obtained within 24 h. Instead of performing multiple experiments, a single DJM-INEPT-INADEQUATE experiment can thus provide a wealth of information for the structural analysis of small molecules.

An Investigation of Weak CH···O Hydrogen Bonds in Maltose Anomers by a Combination of Calculation and Experimental Solid-State NMR Spectroscopy

Two-dimensional (1)H-(13)C MAS-J-HMQC solid-state NMR spectra of the two anomeric forms of maltose at natural abundance are presented. The experimental (1)H chemical shifts of the CH and CH(2) protons are assigned using first-principles chemical shift calculations that employ a plane-wave pseudopotential approach. Further calculations show that the calculated change in the (1)H chemical shift when comparing the full crystal and an isolated molecule is a quantitative measure of intermolecular C-H...O weak hydrogen bonding. Notably, a clear correlation between a large chemical shift change (up to 2 ppm) and both a short H...O distance (<2.7 A) and a CHO bond angle greater than 130 degrees is observed, thus showing that directionality is important in C-H...O hydrogen bonding.

Determination of sugar structures in solution from residual dipolar coupling constants: methodology and application to methyl beta-D-xylopyranoside

We have developed methodology for the determination of solution structures of small molecules from residual dipolar coupling constants measured in dilute liquid crystals. The power of the new technique is demonstrated by the determination of the structure of methyl beta-d-xylopyranoside (I) in solution. An oriented sample of I was prepared using a mixture of C(12)E(5) and hexanol in D(2)O. Thirty residual dipolar coupling constants, ranging from -6.44 to 4.99 Hz, were measured using intensity-based J-modulated NMR techniques. These include 15 D(HH), 4 (1)D(CH), and 11 (n)D(CH) coupling constants. The accuracy of the dipolar coupling constants is estimated to be < +/- 0.02 Hz. New constant-time HMBC NMR experiments were developed for the measurement of (n)D(CH) coupling constants, the use of which was crucial for the successful structure determination of I, as they allowed us to increase the number of fitted parameters. The structure of I was refined using a model in which the directly bonded interatom distances were fixed at their ab initio values, while 16 geometrical and 5 order parameters were optimized. These included 2 CCC and 6 CCH angles, and 2 CCCC and 6 CCCH dihedral angles. Vibrationally averaged dipolar coupling constants were used during the refinement. The refined solution structure of I is very similar to that obtained by ab initio calculations, with 11 bond and dihedral angles differing by 0.8 degrees or less and the remaining 5 parameters differing by up to 3.3 degrees . Comparison with the neutron diffraction structure showed larger differences attributable to crystal packing effects. Reducing the degree of order by using dilute liquid crystalline media in combination with precise measurement of small residual dipolar coupling constants, as shown here, is a way of overcoming the limitation of strongly orienting liquid crystals associated with the complexity of (1)H NMR spectra for molecules with more than 12 protons.

Determination of sugar structures in solution from residual dipolar coupling constants: methodology and application to methyl beta-D-xylopyranoside

We have developed methodology for the determination of solution structures of small molecules from residual dipolar coupling constants measured in dilute liquid crystals. The power of the new technique is demonstrated by the determination of the structure of methyl beta-d-xylopyranoside (I) in solution. An oriented sample of I was prepared using a mixture of C(12)E(5) and hexanol in D(2)O. Thirty residual dipolar coupling constants, ranging from -6.44 to 4.99 Hz, were measured using intensity-based J-modulated NMR techniques. These include 15 D(HH), 4 (1)D(CH), and 11 (n)D(CH) coupling constants. The accuracy of the dipolar coupling constants is estimated to be < +/- 0.02 Hz. New constant-time HMBC NMR experiments were developed for the measurement of (n)D(CH) coupling constants, the use of which was crucial for the successful structure determination of I, as they allowed us to increase the number of fitted parameters. The structure of I was refined using a model in which the directly bonded interatom distances were fixed at their ab initio values, while 16 geometrical and 5 order parameters were optimized. These included 2 CCC and 6 CCH angles, and 2 CCCC and 6 CCCH dihedral angles. Vibrationally averaged dipolar coupling constants were used during the refinement. The refined solution structure of I is very similar to that obtained by ab initio calculations, with 11 bond and dihedral angles differing by 0.8 degrees or less and the remaining 5 parameters differing by up to 3.3 degrees . Comparison with the neutron diffraction structure showed larger differences attributable to crystal packing effects. Reducing the degree of order by using dilute liquid crystalline media in combination with precise measurement of small residual dipolar coupling constants, as shown here, is a way of overcoming the limitation of strongly orienting liquid crystals associated with the complexity of (1)H NMR spectra for molecules with more than 12 protons.

CD14-mediated alterations in transcription and splicing of endogenous retroviruses after injury

Increase in systemic levels of lipopolysaccharide (LPS) contributes to the pathogenesis of distant organ injury after burn. Stress signals elicited from burn influence transcriptional activities of mouse endogenous retroviruses (MuERVs) in various distant organs. The involvement of LPS pathways in the burn-mediated regulation of MuERVs in the spleen was investigated in this study. Spleen harbors substantial numbers of tissue macrophages, a key responder to LPS stimulation. Spleen tissues collected from CD14 (LPS receptor) knockout (KO) and wild type (WT) mice after burn were subjected to RT-PCR analysis of MuERV expression. There was a substantial induction of 2 bands and a marked downregulation of a band in CD14 KO mice compared to WT mice after burn. Sequence analysis of these CD14- and burn-dependent bands identified 3 new alternatively spliced and 2 defective env transcripts of MuERVs as well as novel splicing signals. Chromosomal loci of putative MuERVs sharing the unique U3 sequences of these transcripts were mapped by surveying the entire genome of C57BL/6J mice. In addition, coding potentials, transcriptional regulatory elements, and adjacent cellular genes of these putative MuERVs were analyzed. The results from these studies suggest that injury-triggered LPS/CD14 signaling events play roles in the transcriptional regulation of certain MuERVs carrying unique U3 promoter sequences.

Protein thioacylation: 2. Reagent stability in aqueous media and thioacylation kinetics

Several thioacylating reagents have been tested toward hydrolysis under conditions suitable for protein modifications: 20-35 degrees C and buffered solutions at pH 7.5-8.5. Aliphatic dithioesters are sufficiently stable in aqueous media at room temperature (or below) if protein modification reaction time does not exceed 24 h, whereas at 35 degrees C reaction times must be limited to a few hours. Kinetic data obtained in gelatin thioacylation at room temperature using aliphatic dithioesters and dithio acid are consistent with a second-order reaction rate with respect to amine concentration. The pH dependence of the second-order reaction rate constants indicate that dithioester reacts exclusively with the free amine form of lysine residue, whereas dithiocarboxylate ion reacts with both amine and ammonium ion, probably through a more complex mechanism. Interestingly thioacylation using dithio acids may be obtained in pH near neutrality or in slightly acidic media, thus offering protein modification possibilities at pH 5-9. Thioacylation reaction rates may be expressed as R = -(dAt/dt) = k[H3O+](-b)At2[thioacylating agent] in which At is the amine concentration at time t, constants k and b depending on the reagent nature.

Protein thioacylation. 1. Reagents design and synthesis

Thioacylation is a new way for protein chemical modification. Carboxylic dithioesters and -acids react selectively and rapidly at room temperature with aliphatic amines such as lysine epsilon-amino groups leading to thioamide formation, without any other reagent or catalyst. Various thioacylating reagents were synthesized: monofunctional dithioesters bearing on the acylating end various chemical groups such as: aliphatic chains, phenyl group, mono- and dicarboxylic acids, dialkylphosphonic ester, phosphonic acid, thiol, phenol, or quaternary ammonium group. Bifunctional dithioesters containing either a polymethylene chain or an ethylene oxide oligomer as spacer group as well as some mono- and bis(dithio acids) are described. Applications of thioacylation may be involved either in enzyme chemical modifications or in the obtention of new materials from proteins. Bifunctional reagents might be used as cross-linking or coupling reagents.

Identification of the configuration of neosartorin by long-range nuclear Overhauser effect measurements

The relative configuration of the two xanthene units of neosartorin, a new ergochrome biosynthesised by the soil mould Neosartorya fischeri, was determined using a 1D double-pulsed field gradient spin-echo NOESY experiment. It was found that both units have the same relative stereochemistry. Long-range nonbonding interactions between the substituents of different xanthene units stabilise the nonplanar configuration of the two aromatic rings A and A' connecting both monomer units of neosartorin.

Results of early excision and full-thickness grafting of deep palm burns in children

The timing and method of treatment of deep palm and finger burns varies widely. Our protocol involves performing full-thickness skin grafts (FTSG) in nonhealing palm burns. We reviewed the functional and cosmetic results after FTSG to the palm. From August 1997 to April 1999, 11 patients (12 palms) underwent excision and FTSG within 2 weeks of injury. A panel of medical and nonmedical professionals evaluated follow-up pictures of the grafts at 1, 2 to 4, and beyond 4 months. Parameters used for evaluation were color match with the unburned skin (1 = no difference to 4 = large difference), graft thickness (1 = flat to 4 = markedly raised), overall appearance (1 = poor to 100 = excellent), and time to maturity. Hand function, as assessed by occupational therapy notes, was also recorded. All 12 grafted palms had a 100% take and healed with minimal scarring. Mean color match scores were 2.4 at 1 month, 1.8 at 2 to 4 months, and 1.6 beyond 4 months. On the graft thickness scale, grafts were given scores of 2.6, 2.2, and 1.9 during the same intervals. The overall appearance was 71 at 1 month, 81 at 2 to 4 months, and 85 beyond 4 months. All grafts except 1 were judged to be mature at 2 to 4 months follow-up. Full passive range of motion was attained in all grafted hands within the period of 2 to 4 months after operation. Early excision and FTSG of deep pediatric palm burns can be performed in the outpatient setting. The grafts have an acceptable color match, are minimally raised, and achieve excellent cosmetic result. The grafts mature within a few months after surgery to allow for rapid return to normal range of motion. FTSG should be considered as a first choice for deep palm burns.

A study of creatine kinase reaction in rat brain under chronic pathological conditions-chronic ischemia and ethanol intoxication

Creatine kinase reaction rates were measured by the magnetisation transfer technique in brains of healthy adult and aged rats and in rats with chronic cerebral ischemia and chronic ethanol intoxication. These measurements indicated that the rate constant of the creatine kinase reaction is significantly reduced in the case of severe chronic cerebral ischemia in aged rats. In the adult rats, during chronic ethanol intoxication after 3 weeks of administration of 3 ml of 30% ethanol once a day via a gastric tube, a significant decrease in the pseudo first-order rate constant k(for) of the creatine kinase reaction was also found. In contrast, mild chronic cerebral ischemia in adult rats produced an increase in the reaction rate 4 weeks after occlusion. At the same time, corresponding conventional phosphorus magnetic resonance spectra showed negligible changes in signal intensities.

Radiographic changes after colonoscopic decompression for acute pseudo-obstruction

PURPOSE

Colonoscopy has been the principal tool for decompression in acute colonic pseudo-obstruction, known as Ogilvie's syndrome. The objectives of this study were to determine the immediate effect of colonoscopy on the cecal diameter (measured on supine radiographs) and to delineate possible correlations in the diameters of dilated segments of the colon.

METHODS

The charts and radiographs of 24 patients who had colonoscopic decompression for acute colonic pseudo-obstruction between 1992 and 1997 at the San Diego Veterans Affairs Medical Center and the University of California, San Diego Hospitals were reviewed. We measured cecal, transverse, descending, and sigmoid colon diameters on serial radiographs up to the point of clinical resolution.

RESULTS

Mean +/- standard deviation cecal diameter change (between initial and post-decompression films) was -2+/-3.4 cm at four hours and -2.2+/-3.3 cm one day after decompression. On the daily radiographs between colonoscopic decompression and clinical resolution, there was a close correlation between the diameter of the cecum and that of the transverse colon (P<0.05). There was no correlation between the cecal diameter and that of the descending or sigmoid colon.

CONCLUSIONS

Colonoscopic decompression only causes a small decrease in cecal size in the patient with acute colonic pseudo-obstruction. Dilation patterns of the cecum and transverse colon are significantly correlated in acute colonic pseudo-obstruction. This correlation provides additional support to the contention that the same pathophysiology affects these two segments of the colon.

Multistep denaturation of Borrelia burgdorferi OspA, a protein containing a single-layer beta-sheet

Outer surface protein A (OspA) from the Lyme disease spirochete, Borrelia burgdorferi, is a dumbbell-shaped protein in which two globular domains are connected by a three-stranded beta-sheet segment that is solvent-exposed on both faces. Previous studies showed that the whole protein, including the single-layer beta-sheet, is highly rigid. To elucidate the folding mechanism and the role of the central beta-sheet in the formation of the rigid molecule, we investigated the equilibrium thermal denaturation reaction of OspA. We applied differential scanning calorimetry, heteronuclear NMR spectroscopy, and solution small-angle X-ray scattering (SAXS) to characterize the reaction in detail. All three techniques revealed that OspA denatures in two separable cooperative transitions. NMR measurements on OspA specifically 15N-labeled at Lys residues identified the locations of the two folding units and revealed that the C-terminal segment is less stable than the remaining N-terminal segment. The boundary between the two folding units is located within the central beta-sheet. The interconversion among the three folding states (fully folded, C-terminus unfolded, and fully denatured) is slow relative to chemical shift differences (<24 Hz), indicating that there are significant kinetic barriers in the denaturation reactions. SAXS measurements determined the radius of gyration of the native protein to be 25.0 +/- 0.3 A, which increases to 34.4 +/- 1.0 A in the first transition, and then to 56.1 +/- 1.6 A in the second transition. Thus, the intermediate state, in which the C-terminal folding unit is already denatured, is still compact. These results provide a basis for elucidating the folding mechanism of OspA.

Multistep denaturation of Borrelia burgdorferi OspA, a protein containing a single-layer beta-sheet

Outer surface protein A (OspA) from the Lyme disease spirochete, Borrelia burgdorferi, is a dumbbell-shaped protein in which two globular domains are connected by a three-stranded beta-sheet segment that is solvent-exposed on both faces. Previous studies showed that the whole protein, including the single-layer beta-sheet, is highly rigid. To elucidate the folding mechanism and the role of the central beta-sheet in the formation of the rigid molecule, we investigated the equilibrium thermal denaturation reaction of OspA. We applied differential scanning calorimetry, heteronuclear NMR spectroscopy, and solution small-angle X-ray scattering (SAXS) to characterize the reaction in detail. All three techniques revealed that OspA denatures in two separable cooperative transitions. NMR measurements on OspA specifically 15N-labeled at Lys residues identified the locations of the two folding units and revealed that the C-terminal segment is less stable than the remaining N-terminal segment. The boundary between the two folding units is located within the central beta-sheet. The interconversion among the three folding states (fully folded, C-terminus unfolded, and fully denatured) is slow relative to chemical shift differences (<24 Hz), indicating that there are significant kinetic barriers in the denaturation reactions. SAXS measurements determined the radius of gyration of the native protein to be 25.0 +/- 0.3 A, which increases to 34.4 +/- 1.0 A in the first transition, and then to 56.1 +/- 1.6 A in the second transition. Thus, the intermediate state, in which the C-terminal folding unit is already denatured, is still compact. These results provide a basis for elucidating the folding mechanism of OspA.

NMR studies of Borrelia burgdorferi OspA, a 28 kDa protein containing a single-layer beta-sheet

The crystal structure of outer surface protein A (OspA) from Borrelia burgdorferi contains a single-layer beta-sheet connecting the N- and C-terminal globular domains. The central beta-sheet consists largely of polar amino acids and it is solvent-exposed on both faces, which so far appears to be unique among known protein structures. We have accomplished nearly complete backbone H, C and N and C beta/H beta assignments of OspA (28 kDa) using standard triple resonance techniques without perdeuteration. This was made possible by recording spectra at a high temperature (45 degrees C). The chemical shift index and 15N T1/T2 ratios show that both the secondary structure and the global conformation of OspA in solution are similar to the crystal structure, suggesting that the unique central beta-sheet is fairly rigid.

A stable single-layer beta-sheet without a hydrophobic core

Outer surface protein A from the Lyme disease spirochete Borrelia burgdorferi contains a single-layer beta-sheet connecting the N- and C-terminal globular domains. The central beta-sheet consists largely of polar amino acids and is solvent-exposed on both faces, which so far appears to be unique among known protein structures. We show that the single-layer beta-sheet segment is surprisingly stable (deltaG for hydrogen exchange is approximately 8 kcal mol(-1) at 45 degrees C). Possible factors contributing to the stability of the single-layer beta-sheet are discussed based on an analysis of the crystal structure.

Comparison of a direct and indirect population pharmacodynamic model: application to recombinant human erythropoietin in athletes

Basic physiologic indirect response models have been proposed to account for the pharmacodynamics of drugs that act by way of inhibition or stimulation of the production or loss of endogenous substances or mediators. In this work, these models were applied to account for the effects of recombinant human erythropoietin (rHuEpo) in man. Indeed, rHuEpo induces a delayed increase of serum soluble transferrin receptors (sTfr) and a delayed decrease in ferritin (fr) concentrations. The purpose of the present study was to compare two pharmacodynamic approaches to relate serum erythropoietin (Epo) concentrations to the effect of rHuEpo on sTfr, and fr, the "indirect effect" and the "effect compartment" models. However, due to the average lag time of about 50 hr between the first intake of rHuEpo and the onset of the measurable effects, a delay function was incorporated into the "indirect response models" to describe the relationship between the Epo plasma concentrations and the endogenous receptors or mediators affected by the drug and responsible for the effects on sTfr and fr. There are no real differences in the descriptive features of the two models used. For these reasons, the indirect model seems more appropriate because it supplies a possible mechanistic interpretation of the physiological process.

Cyclodextrins and enantiomeric separations of drugs by liquid chromatography and capillary electrophoresis: basic principles and new developments

Investigation of individual drug enantiomers is required in pharmacokinetic and pharmacodynamic studies of drugs with a chiral centre. Cyclodextrins (CDs) are extensively used in high-performance liquid chromatography as stationary phases bonded to a solid support or as mobile phase additives in HPLC and capillary electrophoresis (CE) for the separation of chiral compounds. We describe here the basis for the liquid chromatographic and capillary electrophoretic resolution of drug enantiomers and the factors affecting their enantiomeric separation. This review covers the use of CDs and some of their derivatives in studies of compounds of pharmacological interest.

Expression of Bombyx family fungal protease inhibitor F from Bombyx mori by baculovirus vector

Fungal protease inhibitor F (FPI-F) from silkworm hemolymph is a novel serine protease inhibitor of the Bombyx family. The cDNA of FPI-F was introduced into a baculovirus vector and a recombinant virus was isolated and plaque-purified. The protease inhibitory activities increased in the culture medium of insect cells and in the hemolymph of silkworms infected with the recombinant virus. Judged from the behavior on ion-exchange and reversed-phase chromatographies, amino acid compositions, amino-terminal sequences, and CD spectra, the recombinant FPI-F was identical with native FPI-F. Infection with the recombinant virus caused inhibition of larval development of the silkworm. However, the degree of the effect was different in two strains, Shinryukaku and Taiheichoan, indicating that the selection of the strain of silkworm is important in using the baculovirus expression system.

A new family of serine protease inhibitors (Bombyx family) as established from the unique topological relation between the positions of disulphide bridges and reactive site

The positions of the reactive site and the disulfide bridges in fungal protease inhibitor F (FPI-F) from silkworm (Bombyx mori), which has a unique amino acid sequence and inhibitory specificity, were investigated. At pH 3.0, subtilisin BPN', which is one of target proteases of this inhibitor, specifically cleaved the peptide bond of the inhibitor at Thr(29)-Val(30). The cleaved bond was regenerated by subtilisin BPN' at pH 8.0. These results indicate that the Thr(29)-Val(30) bond of the inhibitor is the reactive site. The locations of disulfide bridges were determined to be Cys(3)-Cys(35), Cys(14)-Cys(27), Cys(18)-Cys(55), and Cys(37)-Cys(49). Based on the positions of the reactive site and the disulfide bridges, FPI-F is considered to be a member of a new family of serine protease inhibitors. We propose the designation Bombyx family for the new inhibitor family of which FPI-F is a member.

Trypsin and elastase inhibitors from bitter gourd (Momordica charantia LINN.) seeds: purification, amino acid sequences, and inhibitory activities of four new inhibitors

Serine proteinase inhibitors of the squash family were isolated from bitter gourd (Momordica charantia LINN.) seeds by the conventional purification method. Heat treatment of the extract of the seeds allowed removal of large amounts of protein without loss of trypsin and elastase inhibitory activities. From the supernatants thus obtained, the inhibitors were isolated to homogeneity by ion-exchange chromatography, gel filtration, and reversed phase chromatography. One trypsin inhibitor (Momordica charantia trypsin inhibitor-III; MCTI-III) and three elastase inhibitors (Momordica charantia elastase inhibitor-II, -III, and -IV; MCEI-II, -III, and -IV) were newly isolated in addition to trypsin inhibitors MCTI-I and -II and elastase inhibitor MCEI-I previously reported [Hara, S. et. al. (1989). J. Biochem. 105, 88-92]. The primary structures of the four new inhibitors were determined as follows. [sequence: see text] The dissociation constants, Ki, of MCTI-III complex with bovine beta-trypsin, and of MCEI-II, -III, -IV with porcine elastase were determined to be 1.9 x 10(-7) M, 9.4 x 10(-9) M, 4.0 x 10(-9) M, and 4.7 x 10(-9) M, respectively. Although MCTI-III differed from MCTI-I in only two amino acids, having Gly(3) and Gln(13) in place of Arg(3) and Arg(13), the Ki value of MCTI-III was 20-fold larger than that of MCTI-I. Addition of an amino terminal Glu residue, a dipeptide (Glu-Glu-), and a tripeptide (Glu-Glu-Glu-) to MCEI-I strengthened its elastase inhibitory activity by 200-fold.

Sequence analyses and evolutionary relationships among the energy-coupling proteins Enzyme I and HPr of the bacterial phosphoenolpyruvate: sugar phosphotransferase system

We have previously reported the overexpression, purification, and biochemical properties of the Bacillus subtilis Enzyme I of the phosphoenolpyruvate: sugar phosphotransferase system (PTS) (Reizer, J., et al., 1992, J. Biol. Chem. 267, 9158-9169). We now report the sequencing of the ptsI gene of B. subtilis encoding Enzyme I (570 amino acids and 63,076 Da). Putative transcriptional regulatory signals are identified, and the pts operon is shown to be subject to carbon source-dependent regulation. Multiple alignments of the B. subtilis Enzyme I with (1) six other sequenced Enzymes I of the PTS from various bacterial species, (2) phosphoenolpyruvate synthase of Escherichia coli, and (3) bacterial and plant pyruvate: phosphate dikinases (PPDKs) revealed regions of sequence similarity as well as divergence. Statistical analyses revealed that these three types of proteins comprise a homologous family, and the phylogenetic tree of the 11 sequenced protein members of this family was constructed. This tree was compared with that of the 12 sequence HPr proteins or protein domains. Antibodies raised against the B. subtilis and E. coli Enzymes I exhibited immunological cross-reactivity with each other as well as with PPDK of Bacteroides symbiosus, providing support for the evolutionary relationships of these proteins suggested from the sequence comparisons. Putative flexible linkers tethering the N-terminal and the C-terminal domains of protein members of the Enzyme I family were identified, and their potential significance with regard to Enzyme I function is discussed. The codon choice pattern of the B. subtilis and E. coli ptsI and ptsH genes was found to exhibit a bias toward optimal codons in these organisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection of growth-stimulating activity in the proximal small intestine during weaning in the suckling rat

Adaptive changes in enzyme expression and cell proliferation occur in the small intestine of the suckling rat at the beginning of the 3rd postnatal week. This physiological adaptation can be modulated by factors including diet or glucocorticoids. We have previously described an intestinal growth-stimulating fraction derived from the remnant small bowel after resection and found that enteral nutrition is critical for its detection. In view of the similarity between the changes in cell proliferation that occur between 15 and 22 days postnatally and those immediately after resection, we sought to determine whether the small intestinal mucosa of the neonatal rat also contains a similar growth-stimulating fraction. Our results show that extracts of the proximal intestine prepared from 15-day-old rats do contain the growth-stimulating fraction. The activity was not detectable in maternal milk nor in the intestinal extract from 8-day-old rats. When the suckling rats were deprived of solid food, the activity was not detectable in the 15-day-old group. Gel filtration of the acidic extract on a G-25 Sephadex column revealed that the active component is made up of two molecular weight species (approximately 4,500 and 1,500 daltons) similar to that described in the proximal intestine of the postresectional model. These findings suggest that dietary factors may play a role in modulating the proliferative changes that occur at the time of weaning by way of the growth-stimulating fraction.