Search

The fact that most bacteria do not contain a full set of aminoacyl-tRNA synthetases (aaRS) is often underappreciated. In the absence of asparaginyl-tRNA and/or glutaminyl-tRNA synthetase (AsnRS and GlnRS), Asn-tRNAAsn and/or Gln-tRNAGln are produced by an indirect tRNA aminoacylation pathway that relies on misacylation of these two tRNAs by two different misacylating aaRSs, followed by transamidation by an amidotransferase (GatCAB in bacteria). This review highlights the central importance of indirect tRNA aminoacylation to accurate protein translation, mechanistic peculiarities that appear to be unique to this system, and the newly recognized connection between indirect tRNA aminoacylation and mistranslation as a strategy used by bacteria to respond to environmental stressors like antibiotics.

Public opposition to the construction (i.e., siting) of new high voltage overhead transmission lines is not a new or isolated phenomenon. Past research has posited a variety of reasons, applied general theories, and has provided empirical evidence to explain public opposition. The existing literature, while clarifying many elements of the issue, does not yet fully explain the complexities underlying this public opposition phenomenon. The current study demonstrated how two overlooked factors, people’s sense of political efficacy and their familiarity (i.e., prior exposure) with transmission lines, explained attitudes of support and opposition to siting new power lines.

SUMMARY The first cultivated representative of the enigmatic phylum Saccharibacteria (formerly TM7) was isolated from humans and revealed an ultra-small cell size (200–300 nm), a reduced genome with limited biosynthetic capabilities, and a unique parasitic lifestyle. TM7x was the only cultivated member of the candidate phyla radiation (CPR), estimated to encompass 26% of the domain Bacteria. Here we report on divergent genomes from major lineages across the Saccharibacteria phylum in humans and mammals, as well as from ancient dental calculus. These lineages are present at high prevalence within hosts. Direct imaging reveals that all groups are ultra-small in size, likely feeding off commensal bacteria. Analyses suggest that multiple acquisition events in the past led to the current wide diversity, with convergent evolution of key functions allowing Saccharibacteria from the environment to adapt to mammals. Ultra-small, parasitic CPR bacteria represent a relatively unexplored paradigm of prokaryotic interactions within mammalian microbiomes., Graphical Abstract, In Brief McLean et al. show that humans are inhabited by a broad diversity of nanosized bacteria with highly reduced genomes within the Saccharibacteria phylum. They are related to the candidate phyla radiation predominately found in the environment. Saccharibacteria show adaptations and diversification in mammals during their transition from the environment.

The introduction of manmade chemicals, including the herbicide atrazine, into the environment has led to the emergence of microorganisms with new biodegradation pathways. Esquirol et al. demonstrate that the AtzE enzyme catalyzes a central step in atrazine degradation and that expression of AtzE requires coexpression of the small protein AtzG. Remarkably, AtzG and AtzE appear to have evolved from GatC and GatA, components of an ancient enzyme involved in indirect tRNA aminoacylation, providing an elegant demonstration of metabolic repurposing.

Many bacteria lack genes encoding asparaginyl- and/or glutaminyl-tRNA synthetase and consequently rely on an indirect path for the synthesis of both Asn-tRNAAsn and Gln-tRNAGln. In some bacteria such as Thermus thermophilus, efficient delivery of misacylated tRNA to the downstream amidotransferase (AdT) is ensured by formation of a stable, tRNA-dependent macromolecular complex called the Asn-transamidosome. This complex enables direct delivery of Asp-tRNAAsn from the non-discriminating aspartyl-tRNA synthetase to AdT, where it is converted into Asn-tRNAAsn. Previous characterization of the analogous Helicobacter pylori Asn-transamidosome revealed that it is dynamic and cannot be stably isolated, suggesting the possibility of an alternative mechanism to facilitate assembly of a stable complex. We have identified a novel protein partner called Hp0100 as a component of a stable, tRNA-independent H. pylori Asn-transamidosome; this complex contains a non-discriminating aspartyl-tRNA synthetase, AdT, and Hp0100 but does not require tRNAAsn for assembly. Hp0100 also enhances the capacity of AdT to convert Asp-tRNAAsn into Asn-tRNAAsn by ∼35-fold. Our results demonstrate that bacteria have adopted multiple divergent methods for transamidosome assembly and function. Background: Some microorganisms use indirect tRNA aminoacylation to produce Asn-tRNAAsn; the necessary components are assembled into a tRNAAsn-dependent transamidosome complex. Results: A new protein, Hp0100, facilitates formation of an alternative, tRNA-independent transamidosome and increases the efficiency of Asp-tRNAAsn transamidation. Conclusion: Hp0100 is a component of a stable efficient Helicobacter pylori transamidosome. Significance: The Hp0100-containing transamidosome allows for optimal indirect biosynthesis of Asn-tRNAAsn.

An absorption-mode Fourier transform ion cyclotron resonance (FT-ICR) mass spectrum exhibits two types of baseline distortion: a slow periodic oscillation even where no signal peaks are present, and additional distortion near signal peaks and proportional to signal magnitude. These distortions interfere with automated peak-picking, unless the baseline systematic variation is much less than baseline rms random noise. We previously showed that the slow oscillation is removed by low-pass filtering. Here, we present a fast, robust, and automated algorithm that flattens the absorption-mode spectral baseline, even in the vicinity of signal peaks. The method begins by defining baseline data values, followed by linear interpolation to generate baseline data values between the defined values, then boxcar smoothing to generate a final baseline spectrum, and final subtraction of that baseline from the original spectrum to yield a baseline-flattened absorption-mode spectrum. We apply the algorithm to a crude oil spectrum (with 8000 peaks) and to a ribonuclease A protein spectrum (with multiply-charged ion isotopic distributions). We identify many more peaks (crude oil) without loss of mass accuracy, and obtain more accurate isotopic distributions (RNase A).

The link between child/adolescent aggression and substance use is an important area of study, as child aggression is a strong risk factor for substance use — a major public health concern for which few successful interventions are available. A better understanding of the link between aggression and substance use could help to refine and develop more effective and perhaps more targeted prevention and intervention strategies. One way to further understand the link between aggression and substance use may be to distinguish between proactive and reactive functions of aggression. Indeed, there is growing evidence to suggest that proactively aggressive behavior is more strongly linked to substance use, particularly problem drinking, than reactive aggression. However, further investigation is needed to fully understand these associations. This paper presents a thorough review of the available research, outlines gaps in the literature, and offers suggestions for future research.

At sufficiently high mass accuracy, it is possible to distinguish phosphorylated from unmodified peptides by mass measurement alone. We examine the feasibility of that idea, tested against a library of all possible in silico tryptic digest peptides from the human proteome database. The overlaps between in silico tryptic digest phosphopeptides generated from known phosphorylated proteins (1–12 sites) and all possible unmodified human peptides are considered for assumed mass error ranges of ±10, ±50, ±100, ±1000, and ±10,000 ppb. We find that for mass error ±50 ppb, 95% of all phosphorylated human tryptic peptides can be distinguished from nonmodified peptides by accurate mass alone throughout the entire nominal mass range. We discuss the prospect of on-line LC MS/MS to identify phosphopeptide precursor ions in MS1 for selected dissociation in MS2 to identify the peptide and site(s) of phosphorylation.

Emergent reversal of oral anticoagulation (OAC), including vitamin K antagonist (VKA) and direct-acting oral anticoagulant (DOAC) therapy, continues to be an important aspect of OAC due to the potential for serious bleeding events. Four-factor prothrombin complex concentrate (4F-PCC) is commonly

Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry relies upon linearity between the ion cyclotron excitation and the observed response. However, nonlinearities result from non-ideal applied electric and magnetic fields and Coulombic interactions. Here, we report nonlinear response at low excitation electric field magnitude due to Coulombic shielding. The measured ICR signal magnitude exhibits an excitation voltage threshold that increases monotonically with the number of shielding ions (i.e., unexcited ions). If shielding ions are not present, ICR signal magnitude versus excitation voltage is linear (e.g., for quadrupole-isolated ions of nearly a single m/z). Finally, we show that shielding results in a reduced cyclotron radius at low excitation voltage, resulting in an increased rate of transient decay; thereby exacerbating response nonlinearity and excitation threshold for long data acquisition period.

Eukaryotic proteins can be post-translationally modified with a glycosylphosphatidylinositol (GPI) membrane anchor. This modification reaction is catalyzed by GPI transamidase (GPI-T), a multimeric, membrane-bound enzyme. Gpi8p, an essential component of GPI-T, shares low sequence similarity with caspases and contains all or part of the enzyme's active site [U. Meyer, M. Benghezal, I. Imhof, A. Conzelmann, Biochemistry 39 (2000) 3461-3471]. Structural predictions suggest that the soluble portion of Gpi8p is divided into two domains: a caspase-like domain that contains the active site machinery and a second, smaller domain of unknown function. Based on these predictions, we evaluated a soluble truncation of Gpi8p (Gpi8(23-306)). Dimerization was investigated due to the known proclivity of caspases to homodimerize; a Gpi8(23-306) homodimer was detected by native gel and confirmed by mass spectrometry and N-terminal sequencing. Mutations at the putative caspase-like dimerization interface disrupted dimer formation. When combined, these results demonstrate an organizational similarity between Gpi8p and caspases.

Electron capture dissociation (ECD) efficiency in a 9.4 T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer varies periodically with the time interval between ion and electron injection. The observed modulation frequency correlates to within 1% with ion magnetron frequency, most probably due to misalignment between the ion beam and the electron beam. The optimum ECD conditions are obtained by correctly phasing electron injection with the ion magnetron motion. Displacement of the trapped ion cloud by variation of the ICR trap radial electric field decreases ECD efficiency modulation amplitude. Experiments directly suggest that only ions interacting with electrons at the moment of electron injection participate in ECD reactions.

This report presents reliability, validity and sensitivity indices for the Motivational Interviewing Treatment Integrity (MITI) scale. Factor analysis of MI treatment sessions coded with the Motivational Interviewing Skills Code (MISC) was used to derive 10 elements of MI practice, forming the MITI. Canonical correlation revealed that the MITI captured 59% of the variability in the MISC. Reliability estimates for the MITI were derived using three masked, independent coders. Intra-class coefficients ranged from .5 to .9 and were generally in the good to excellent range. Comparison of MITI scores before and after MI workshops indicate good sensitivity for detecting improvement in clinical practice as result of training. Implications for the use of this instrument in research and supervision are discussed.

We have measured the wavelength resolved fluorescence emission laser-induced fluorescence (LIF) spectrum of C 6 F 3 H 3 + confined in an open cylindrical ion cyclotron resonance Penning trap. Ion cyclotron resonant azimuthal quadrupolar excitation successfully mass-selects and traps the ions for 10 s for repeated laser interrogation, and establishes that the observed fluorescence is from C 6 F 3 H 3 + ions. Electron-induced fluorescence (EIF) emission spectra of the same species were acquired for comparison. Vibrational structure was resolved for both LIF and EIF, and our assignments are consistent with prior literature values in the absence of ion trapping and high magnetic field (3 T). This work represents the first determination of wavelength resolved LIF emission spectra of organic ions in a Penning trap.

Dimensional control of composite components is critical for cost effective manufacturing of large composite aerospace structures. This paper presents an engineering approach to the prediction of process-induced deformations of three-dimensional (3D) autoclaved composite components. A 6-step method that uses a two-dimensional (2D) special purpose finite element (FE) based process simulation code and a standard 3D structural FE code is presented. The approach avoids the need to develop a full 3D process model, significantly reducing the computational effort yet retaining much of the detail required for accurate analysis. The methodology is presented together with numerical examples and two case studies demonstrating the validity, utility, and limitations of the approach.

Fourier transform ion cyclotron resonance mass spectrometry is based on image current detection of coherently excited ion cyclotron motion. The detected signal magnitude and peak shape may be understood from idealized behavior: single ion, zero-pressure, spatially uniform magnetic field, three-dimensional axial quadrupolar electrostatic trapping potential, and spatially uniform resonant alternating electric field. In practice, deviation from any of the above conditions will shift, distort, split, and/or coalesce FT-ICR mass spectral peaks. Fortunately, such peak distortions may typically be avoided by appropriate experimental design and/or greatly minimized by internal frequency-to-m/z calibration. Various aspects of modern FT-ICR detection (hardware and software) are discussed.

Aminoacyl tRNA synthetases (aaRSs) catalyze the first step in protein biosynthesis, establishing a connection between codons and amino acids. To maintain accuracy, aaRSs have evolved a second active site that eliminates noncognate amino acids. Isoleucyl tRNA synthetase edits valine by two tRNA Ile -dependent pathways: hydrolysis of valyl adenylate (Val-AMP, pretransfer editing) and hydrolysis of mischarged Val-tRNA Ile (posttransfer editing). Not understood is how a single editing site processes two distinct substrates—an adenylate and an aminoacyl tRNA ester. We report here distinct mutations within the center for editing that alter adenylate but not aminoacyl ester hydrolysis, and vice versa. These results are consistent with a molecular model that shows that the single editing active site contains two valyl binding pockets, one specific for each substrate.

The laser-induced fluorescence (LIF) excitation spectrum of gas-phase hexafluorobenzene cations (C6F6+) has been measured at room temperature, by ion trapping and cyclotron frequency-based mass-selection. The optical spectral resolution, vibrational state assignments, and their corresponding wavelengths compare favorably to prior data [J. Chem. Phys. 70 (1979) 138]. The present approach offers a general entry into optical spectroscopy of collisionally stable gas-phase ions.

Electrosprayed protein ions are accumulated and mass selected in an external linear octopole trap before injection into a Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Mass selection is performed by application of superimposed rf and dc octopole electric potentials during ion accumulation. Ion trajectory stability and mass selection in the octopole field are explained qualitatively by analogy to a quadrupole mass filter. Accumulation of ions from a selected m/z range is demonstrated experimentally for 7 and 9.4 T electrospray ionization (ESI) FTICR mass spectrometers. Ion fragmentation in the octopole may occur under certain operating conditions.

Misactivation of amino acids by aminoacyl-tRNA synthetases can lead to significant errors in protein synthesis that are prevented by editing reactions. As an example, discrete sites in isoleucyl-tRNA synthetase for amino acid activation and editing are about 25 A apart. The details of how misactivated valine is translocated from one site to the other are unknown. Here, we present a kinetic study in which a fluorescent probe is used to monitor translocation of misactivated valine from the active site to the editing site. Isoleucine-specific tRNA, and not other tRNAs, is essential for translocation of misactivated valine. Misactivation and translocation occur on the same enzyme molecule, with translocation being rate limiting for editing. These results illustrate a remarkable capacity for a specific tRNA to enhance amino acid fine structure recognition by triggering a unimolecular translocation event.

The gas-phase hydrogen/deuterium exchange of [M + n H] n + ( n = 5–13) ions of bovine ubiquitin with the H/D exchange reagent D 2 O are examined by electrospray ionization Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. All of the odd or all of the even charge states were isolated by stored waveform inverse Fourier transform excitation and simultaneously reacted with D 2 O leaked steadily into the ICR cell for reaction periods ranging from 1 s to 1 h. Different gas-phase protein conformations could be resolved according to difference in extent of H/D exchange. The 5+ and 6+ charge states display broad distributions of conformations ranging from 0–80% deuterium incorporation. In contrast, each of the higher charge states, 7–11+ and 13+, displays a single major isotopic distribution, whereas the 12+ charge state separates into two isotopic distributions of comparable abundance. In general, H/D exchange rates decrease with increasing charge state. External electrospray ionization source conditions (capillary current and external accumulation period) were varied while observing the conformational distribution of the 7+ charge state: increased heating in either region reduced the number of slow-exchanging conformations. At 9.4 T, it is possible to trap a large number of ions for a long reaction period (up to 1 h) at relatively high pressure (2 × 10 −7 Torr). These results demonstrate the capability of FT-ICR mass analysis following gaseous H/D exchange of electrosprayed proteins to disperse different gas-phase protein conformations for subsequent isolation and characterization.

We develop and then empirically test a model of how organization reputation, job and organizational attributes, and recruiter behaviors influence applicant attraction to firms using data from 361 campus recruitment interviews in which applicants completed surveys before and after the interview. Results indicate that recruiter behaviors did not have a direct effect on applicant attraction, but influenced attraction indirectly through influencing perceptions of job and organizational attributes. As hypothesized, job and organizational attributes positively influenced attraction, and organization reputation positively influenced applicant perceptions of job and organizational attributes and recruiter behaviors. Contrary to our hypotheses, however, organization reputation had a negative direct effect on applicant attraction. We discuss implications of our findings and suggest directions for future research.

Azimuthal quadrupolar excitation has become one of the most useful techniques for ion axialization and translational cooling for FT-ICR mass spectrometry, leading to order(s)-of-magnitude improvement in mass selectivity, resolving power, mass accuracy, remeasurement efficiency, etc. Recently, Hendrickson et al. (J. Am. Soc. Mass Spectrom. 6 (1995) 448–452) showed that axialization may be achieved by 2-plate azimuthal quadrupolar excitation, in which an rf voltage of the same amplitude and phase is applied to a single pair of opposed side electrodes, while grounding the other orthogonal opposed pair (rather than applying an rf voltage of equal amplitude but shifted in phase by 180° to the second pair as in prior 4-plate experiments). Here, we analyze theoretically and test experimentally the performance of these two electrode geometries. As previously shown, either geometry can achieve axialization by resonant excitation at the unshifted ion cyclotron frequency, (ωc = qB/m). For either excitation configuration, excitation at twice the reduced cyclotron frequency, 2ω+, leads to unwanted exponential growth of the ion cyclotron radius. For 2-plate geometry, we show that excitation at twice the axial oscillation frequency, 2 ωz, leads to exponential growth in z-oscillation amplitude, whereas excitation at ωc = ω+ + ω− and ωp = ω+ − ω− (‘parametric’ frequency) leads to complex ion behavior. Finally, we discuss the effect of azimuthal quadrupolar excitation amplitude (as well as frequency) on axialization.

Trapping of ions in the electron beam of a FTICR mass spectrometer is investigated and a simple model describing the confinement process is presented. Detection of resistive-wall destabilization of the magnetron motion of ions in the trapped-ion cell is used to determine conditions for ion trapping within and escape from the electron beam. The model predicts a potential well that is dependent on electron beam current, energy, and dimension in defining its capacity for low energy ions. Plots of ion retention time versus ion number are consistent with a model in which ions are initially trapped in the electron beam but with increasing ion formation will eventually overcome the potential depression in the electron beam and escape into magnetron orbits. Based upon this model, expressions are derived for ion retention time which are then fit to the experimental data. The model is used to estimate ion number, initial magnetron radius and ion cloud shape and density. One example in which electron trapping is important in the FTICR experiment is in the efficient transfer of ions between dual trapped-ion cells. Ion transfer within the potential depression of the electron beam environment is shown to be virtually 100% efficient over a 10 ms interval whereas all ions are lost to collisions with the conductance limit after 2 ms when transferring without the confining aid of the electron beam. Several analytical applications of electron traps in the ICR cell are now being investigated.

Leucine enkephalin (Leu-enk) was coupled to both T and B cell antibodies in order to investigate the possibility of enhanced immunogenicity via targeted immunization. The two antibodies used were Hm × Mo CD3 and Gt × Mo Ig, respectively. The data indicate that while both antibody carriers enhanced the immunogenicity of Leu-enk, the use of the Hm × Mo CD3 antibody resulted in a greater number of mice with positive Leu-enk specific serum titers. 12 Leu-enk cell lines were produced and one, LE4H8, was chosen for characterization.

An experiment was conducted to relate the effectiveness of N-(n-butyl)thiophosphoric triamide (NBPT) and its oxon analog N-(n-butyl)phosphoric triamide (BNPO) in controlling urea hydrolysis in soils to their corresponding soil concentrations. Both compounds were applied to an acid soil (pH 4.9) and to the same soil that had been neutralized (pH 7.1) by long-term liming or by the recent application of Ca(OH)2. Hydrolysis of urea applied with the inhibitors was monitored along with the disappearance of the compounds themselves. Both compounds controlled urea hydrolysis much more effectively in the neutral soils than in the acid soil. HPLC analysis of soil extracts demonstrated that both compounds disappeared more rapidly in the acid soil, and that the compounds disappeared at similar rates for both neutral soils, indicating that pH governed disappearance rates in these soils. Disappearance rates were generally first-order for both compounds, although NBPT disappeared at an accelerated rate at low concentrations, presumably due to its simultaneous conversion to BNPO. The effectiveness of both compounds in controlling urea hydrolysis was closely related to the concentrations of BNPO found in the soil. BNPO was generally maintained at higher concentrations following NBPT application than when BNPO was applied directly to soil.

The initiation and growth of coherent magnetron motion for ions injected into a Fourier transform ion cyclotron resonance trapped ion cell is investigated. The phenomenon is demonstrated for laser desorption/ionization (LDI) of metals and salts and for electrospray ionization (ESI) of multiply charged proteins. In all cases, the rate of growth of the magnetron orbit increases proportionally with trap potential, ion density, and external detection circuit resistance. The data support resistive damping of the magnetron motion as the primary relaxation mechanism leading to ion ejection from the cell within time periods ranging from a few hundred milliseconds to tens of seconds. Factors associated with ion injection that contribute to initiation and growth of the destabilizing motion are length of the injection period relative to the magnetron period and extent of off-axis injection. In general, if the injection period is smaller than one period of the magnetron motion, as is the case for LDI, and the injection point is severely off the centerline of the cell, coherent growth is observed instantaneously and ions are expelled from the cell within a few hundred milliseconds. If the LDI ions are introduced along the centerline, coherent motion leading to expulsion is still observed but initiation times increase ten-fold. For the case in which ESI ions focused along the centerline are injected into the trap for a time much longer than the period of a magnetron oscillation, initiation and growth of coherent magnetron is only observed at much longer times and with a larger trap potential.

A new feedback system has been developed that stabilizes the SLC beams at many locations. The feedback loops are designed to sample and correct at the repetition rate of the accelerator. Each loop can be distributed across several INTEL 80386 microprocessors that control the SLC hardware. A new communications system, KISNET, has been developed to pass data between the microprocessors at this rate. The software is written using the state space formalism of digital control theory and is database driven. This allows a new feedback loop to be implemented by setting up the on-line database and perhaps installing a communications link. Eighteen such loops have now been implemented and this has measurably improved the performance of the accelerator.

The trapping of metal ions in laser desorption/ionization (LDI) Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry is attributed to an electrostatic shielding mechanism promoted by the sustained quasi-neutral plasma behavior of the desorbed particle plume in strong magnetic fields. This shielding process allows low energy ions to penetrate the applied trapping potentials at the trapped-ion cell, thus resulting in the introduction of ions with energies less than the effective depth of the trapping potential well. Subsequent deshielding of these ions while in the cell exposes them to the trapping field and results in their retention. Data from time-of-flight (TOF) studies indicate that large spatially and temporally overlapped populations of high energy ions and low energy electrons are generated by LDI of a variety of metal targets when laser power density exceeds 107–108W cm−2. The charge density in the desorbed plasma is shown to increase during flight along converging magnetic field lines but to dissipate rapidly on exiting the field. Retarding potential studies in the magnetic field performed with both TOF and FT-ICR detection indicate that the Debye shielding exhibited by these quasi-neutral populations is sufficient in some cases to allow ions with energies on the order of 1 eV to penetrate retarding potentials as high as 500 V. Further indication that such effects are present in the LDI FT-ICR experiment is given by TOF kinetic energy analysis of ions acquired in the trapped-ion cell from LDI and then dumped to an external detector. This analysis indicates that the average kinetic energy of such ions is typically only 60% of the applied trapping potential.

Two novel hexacyclic norsesterterpene alkaloids, kimbasines A and B, have been isolated from cytotoxic extracts of the sponge Igernella notabilis . The structures, related as butyrate and acetate esters, were solved by analyses of spectral data of kimbasine A and comparison of data for kimbasine B with those of kimbasine A. Biological testing data for kimbasine A are presented.

HPLC-purified N-(n-butyl)thiophosphoric triamide (NBPT) had no delectable urease inhibitory activity when tested with jack bean urease. However, considerable inhibition was associated with soil extracts when NBPT had been exposed in the soils for several hours. This activity was due to an NBPT derivative that was isolated by reverse phase HPLC. with NBPT and the derivative detected by a postcolumn system based on acid hydrolysis and phosphomolybdate complex formation. The purified derivative was shown to be highly active, giving 50% inhibition of jack bean urease at a concentration between 10 and 100 nM. Mass spectral analysis revealed the active derivative to be N-(n-butyl) phosphoric triamide. the oxon analog of NBPT.

Codon-specific incorporation of noncoded amino acids into proteins can diversify the genetic code. Now, in both E. coli and S. cerevisiae, iterative rounds of selection can be used to isolate aminoacyl-tRNA synthetases that aminoacylate suppressor tRNAs with noncoded amino acids.

A reinvestigation of the diterpene constituents of the sea pen Ptilosarcus gurneyi was undertaken in order to clarify the stereochemistry of ptilosarcone and ptilosarcenone. In the course of reisolating those two compounds, five new briaran diterpenes were uncovered and identified. The structures and stereochemical assignments in the whole group have been established by spectroanalytical methods. Insecticidal screening of three of the compounds against the tobacco hornworm, Manduca sexta , revealed either toxicity or a reduction in weight gain.

Trace metal bioavailability and mobility in soil systems is a function of both the metal speciation in the soil solution and the distribution of metals between solid soil components and the soil solution. A method has been developed to quantify metal speciation in sludge-amended soils which requires extraction of the soil with 0.01 M Ca(NO 3 ) 2 , 0.01 M CaCl 2 , and 0.01 M Ca(NO 3 ) 2 plus 5 × 10 −5 M Na 2 EDTA. This method was applied to a silt loam surface soil amended with 408 T ha −1 (20%) of a sludge containing high concentrations of trace metals. Calculations showed that, of the Cd, Zn, Cu, Ni, and Fe in solution, 80, 54, 0.7, 0.03, and 10 −4.7 % were present as uncomplexed ions, respectively. Logarithms of the relative stability constants with respect to Cd (K Cd M ) calculated for the naturally occurring soluble complexing agents present in the Ca(NO 3 ) 2 extract were −0.55, −2.69, −3.85, and −7.80 for Zn, Cu, Ni, and Fe, respectively. Relative stability constants calculated with respect to Cd for the solid phase yielded similar values for the respective metals.

The effectiveness of Nitrapyrin (NI) as a nitrification inhibitor is largely determined by the rate at which it is hydrolyzed. A procedure was developed in which Cl − liberated during NI hydrolysis was used to follow NI degradation in laboratory studies. The procedure allowed determination of Cl − from as little as 0.5 mg·l −1 Nitrapyrin and permitted analysis of up to 20 samples h −1 . The method must be restricted to experiments where background Cl −1 can be either removed by leaching or corrected for by use of control samples. Temperature was the most important factor affecting NI hydrolysis and the process was not biologically-mediated. The rate of hydrolysis was not affected by pH in the range 2.7–11.9, or by sorption on colloidal surfaces providing the surfaces remained in contact with the solution. Hydrolysis was slower in a soil at field moisture capacity than at saturation. The findings also showed that experiments conducted in containers with lipophilic components (e.g. rubber or polyethylene) may be suspect due to sorption of NI.

The aerobic incubation procedures commonly used in biological studies have several disadvantages to assess inhibition of nitrification. Therefore, a more suitable procedure was developed. It involves pre-incubating soil samples treated with (NH4)2HPO4 to establish a uniform population of nitrifiers before the addition of the nitrification inhibitor or other amendments. Through successive additions of (NH4)2HPO4, a constant nitrification rate is maintained. This system enables direct comparison between treatments throughout the experiment. Data obtained using this procedure indicated that sorption of Nitrapyrin (NI) is a major factor decreasing the effectiveness of NI in organic soils. Loss of NI by volatilization also decreased its effectiveness, while the relative inhibition by NI was found to increase as soil pH increases. The greater susceptibility of nitrifiers to NI at high pH may be due to a relationship between pH and nitrifier ecology.

A novel antimicrobial pyranone has been obtained from the very polar extracts of the encrusting gorgonian Briareum polyanthes . Spectroanalytical and chemical methods were used to develop two possible structures; x-ray diffraction studies established the structure and relative stereochemistry.

Studies with the urease inhibitor phenylphosphorodiamidate (PPO) showed that PPD activity rapidly diminished following incubation in soil at 35°C, but upon continued incubation gave inhibition equivalent to that shown initially. Subsequent studies demonstrated that the gradual increase in activity was due to PPD decomposition to phenol. Direct application of similar molar quantities of phenol gave an identical pattern of inhibition, although offset by 3 days, as that observed with PPD. The level of inhibition observed with phenol was somewhat greater than that obtained for catechol, the anticipated reaction product.