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Prominent physiological mechanisms that sustain cochlear function across a lifetime in the face of noise stress are highlighted. Central to this are humoral and intracellular processes protecting the mechanotransducer apparatus, and sustaining neurotransmission across the cochlear hair cell – spiral ganglion afferent synapse. At the level of the cochlear partition, ‘purinergic hearing adaptation’ desensitises cochlear hair cell – mediated sound transduction, protecting the hair cells and their afferent synapses from sustained noise stress. Within hair cells, Ca2+ buffering and active extrusion are central to mechanotransducer function and control of glutamatergic neurotransmission. With acoustic hyperstimulation plasticity in pre-synaptic and post-synaptic specialisations, particularly structural and molecular responses of ribbon complexes likely mitigate synaptopathy.

We present UV, optical, and NIR photometry of the first electromagnetic counterpart to a gravitational wave source from Advanced LIGO/Virgo, the binary neutron star merger GW170817. Our data set extends from the discovery of the optical counterpart at $0.47$ days to $18.5$ days post-merger, and includes observations with the Dark Energy Camera (DECam), Gemini-South/FLAMINGOS-2 (GS/F2), and the {\it Hubble Space Telescope} ({\it HST}). The spectral energy distribution (SED) inferred from this photometry at $0.6$ days is well described by a blackbody model with $T\approx 8300$ K, a radius of $R\approx 4.5\times 10^{14}$ cm (corresponding to an expansion velocity of $v\approx 0.3c$), and a bolometric luminosity of $L_{\rm bol}\approx 5\times10^{41}$ erg s$^{-1}$. At $1.5$ days we find a multi-component SED across the optical and NIR, and subsequently we observe rapid fading in the UV and blue optical bands and significant reddening of the optical/NIR colors. Modeling the entire data set we find that models with heating from radioactive decay of $^{56}$Ni, or those with only a single component of opacity from $r$-process elements, fail to capture the rapid optical decline and red optical/NIR colors. Instead, models with two components consistent with lanthanide-poor and lanthanide-rich ejecta provide a good fit to the data, the resulting "blue" component has $M_\mathrm{ej}^\mathrm{blue}\approx 0.01$ M$_\odot$ and $v_\mathrm{ej}^\mathrm{blue}\approx 0.3$c, and the "red" component has $M_\mathrm{ej}^\mathrm{red}\approx 0.04$ M$_\odot$ and $v_\mathrm{ej}^\mathrm{red}\approx 0.1$c. These ejecta masses are broadly consistent with the estimated $r$-process production rate required to explain the Milky Way $r$-process abundances, providing the first evidence that BNS mergers can be a dominant site of $r$-process enrichment., 13 Pages, 3 Figures, 2 Tables. ApJL, In Press. Keywords: GW170817, LVC

There is considerable interest in both soy and canola as biodiesel feedstock crops because of the net reduction in CO 2 emissions resulting from the use of biodiesel in place of petroleum diesel. Whether these two crops differ in net CO 2 savings is unknown, in part because of our ignorance of their impact on soil C. We, therefore, monitored soil C for three years in an experiment that included both soy and canola rotations. We found that soil C concentrations were significantly lower under canola than soy, and that the difference represented as much as 64% of the C savings of soy biodiesel over petroleum diesel. We tested two hypotheses that could explain this difference in soil C. First, because canola can acidify the soil, we determined whether a reduction in inorganic C (as carbonate) in canola plots could account for the soil C difference. Carbonate concentration did not differ significantly in soy and canola plots. Second, we determined whether soil organic matter concentration could account for the soil C difference. Soil organic matter concentration was significantly lower in canola than in soy plots, accounting for the difference in soil C. We further hypothesized that because soy is mycorrhizal and canola is not, soy soils should contain higher concentrations of glomalin, a recalcitrant substance produced by mycorrhizal fungi, and that this could help to explain the difference in soil organic matter. Glomalin concentrations were significantly lower in canola plots, but this difference accounted for only a fraction of the total soil C difference. Our results suggest that a proper accounting of life cycle C savings of biodiesel when used in place of petroleum diesel must consider soil C.

The results of a world-wide coordinated observational campaign on the broad-lined Type Ic SN 2003jd are presented. In total, 74 photometric data points and 26 spectra were collected using 11 different telescopes. SN 2003jd is one of the most luminous SN Ic ever observed. A comparison with other Type Ic supernovae (SNe Ic) confirms that SN 2003jd represents an intermediate case between broad-line events (2002ap, 2006aj), and highly energetic SNe (1997ef, 1998bw, 2003dh, 2003lw), with an ejected mass of M_{ej} = 3.0 +/- 1 Mo and a kinetic energy of E_{k}(tot) = 7_{-2}^{+3} 10^{51} erg. SN 2003jd is similar to SN 1998bw in terms of overall luminosity, but it is closer to SNe 2006aj and 2002ap in terms of light-curve shape and spectral evolution. The comparison with other SNe Ic, suggests that the V-band light curves of SNe Ic can be partially homogenized by introducing a time stretch factor. Finally, due to the similarity of SN 2003jd to the SN 2006aj/XRF 060218 event, we discuss the possible connection of SN 2003jd with a GRB.

We present the final installment of an intensive 13-year study of variations of the optical continuum and broad H-beta emission line in the Seyfert 1 galaxy NGC 5548. The data base consists of 1530 optical continuum measurements and 1248 H-beta measurements. The H-beta variations follow the continuum variations closely, with a typical time delay of about 20 days. However, a year-by-year analysis shows that the magnitude of emission-line time delay is correlated with the mean continuum flux. We argue that the data are consistent with the simple model prediction that the size of the broad-line region is proportional to the square root of the ionizing luminosity. Moreover, the apparently linear nature of the correlation between the H-beta response time and the nonstellar optical continuum arises as a consequence of the changing shape of the continuum as it varies, specifically with the optical (5100 A) continuum luminosity proportional to the ultraviolet (1350 A) continuum luminosity to the 0.56 power.

We report measurements of the mass density, Omega_M, and cosmological-constant energy density, Omega_Lambda, of the universe based on the analysis of 42 Type Ia supernovae discovered by the Supernova Cosmology Project. The magnitude-redshift data for these SNe, at redshifts between 0.18 and 0.83, are fit jointly with a set of SNe from the Calan/Tololo Supernova Survey, at redshifts below 0.1, to yield values for the cosmological parameters. All SN peak magnitudes are standardized using a SN Ia lightcurve width-luminosity relation. The measurement yields a joint probability distribution of the cosmological parameters that is approximated by the relation 0.8 Omega_M - 0.6 Omega_Lambda ~= -0.2 +/- 0.1 in the region of interest (Omega_M 0) = 99%, including the identified systematic uncertainties. The best-fit age of the universe relative to the Hubble time is t_0 = 14.9{+1.4,-1.1} (0.63/h) Gyr for a flat cosmology. The size of our sample allows us to perform a variety of statistical tests to check for possible systematic errors and biases. We find no significant differences in either the host reddening distribution or Malmquist bias between the low-redshift Calan/Tololo sample and our high-redshift sample. The conclusions are robust whether or not a width-luminosity relation is used to standardize the SN peak magnitudes.

Apremilast, a small molecule specific inhibitor of phosphodiesterase 4, works intracellularly to modulate pro-inflammatory and anti-inflammatory mediators. This phase II, multicenter, open-label study evaluated the efficacy, tolerability, and pharmacodynamics of apremilast in patients with recalcitrant plaque psoriasis.BRThis multicenter, open-label study comprised four phases: pre-treatment (≤35 days), treatment (12 weeks), extension (12 weeks), and observational follow-up (4 weeks). Patients with recalcitrant plaque psoriasis received apremilast 20 mg BID for 12 weeks. Responders (≥75% improvement in Psoriasis Area and Severity Index [PASI-75]) continued treatment and non-responders (PASI-75) were titrated to apremilast 30 mg BID through week 24. Efficacy assessments included change in static Physician's Global Assessment, PASI, and body surface area, and proportion of patients achieving PASI-50, PASI-75, and PASI-90. Other assessments included adverse events, lesional skin biopsies to assess changes in epidermal thickness, and immunohistochemistry to assess changes in peripheral blood subsets.A total of 30 patients were enrolled. At week 12, 67% of patients had a ≥1-point improvement in static Physician's Global Assessment, meeting treatment effect criterion. Mean percent decreases (improvements) from baseline were -59% for PASI score and -53% for body surface area. Most adverse events were mild. Median reduction in epidermal thickness was 34% at week 12 (P=0.083); five patients showed absence of keratin 16. Significant reductions in CD11c, CD3, and CD56 indicate that apremilast reduced myeloid dendritic cell, T-cell, and NK-cell or NK-T-cell infiltration into the epidermis and dermis. Reduced inflammatory leukocytes, with a pattern of broad, partial inhibition, suggested reduced IL-23/Th17 and Th22 response pathways.These results confirm apremilast's biological and clinical activity and support ongoing studies in psoriasis. Clinicaltrials.gov Identifier: NCT00521339.

We present near infra-red light curves of supernova (SN) 2011fe in M101, including 34 epochs in H band starting fourteen days before maximum brightness in the B-band. The light curve data were obtained with the WIYN High-Resolution Infrared Camera (WHIRC). When the data are calibrated using templates of other Type Ia SNe, we derive an apparent H-band magnitude at the epoch of B-band maximum of 10.85 \pm 0.04. This implies a distance modulus for M101 that ranges from 28.86 to 29.17 mag, depending on which absolute calibration for Type Ia SNe is used., 9 pages, 3 figures, emulateapj style, accepted for publication in The Astrophysical Journal

Summary The sec Y gene from Sulfolobus acidocaldarius has been cloned and sequenced. It codes for a putative protein containing 463 amino acids. Computer analysis of the protein sequence indiates 10 possible hydrophobic segments that could be located in transmembrane regions as has been shown for other Sec Y proteins. The protein shows substantial amino acid sequence identity to other archaeal Sec Y proteins ( M. vannielii and H. marismortui ). When this archaeal protein is compared to the Sec Y protein in bacteria and eucarya there is significantly more sequence similarity to the eucaryal Sec Y protein than to the bacterial equivalent.

The ribosomal L12 protein gene of Sulfolobus solfataricus (SsoL12) has been subcloned and overexpressed in Escherichia coli. Five protein L12 mutants were designed: two NH2-terminal and two COOH-terminal truncated mutants and one mutant lacking the highly charged part of the COOH-terminal region. The mutant protein genes were overexpressed in E. coli and the products purified. The amino acid composition was verified and the NH2 terminally truncated mutants were subjected to Edman degradation. The SsoL12 protein was selectively removed from entire S. solfataricus ribosomes by an ethanol wash. The remaining ribosomal core particles showed a substantial decrease in the in vitro translational activity. S. solfataricus L12 protein overexpressed in E. coli (SsoL12e) was incorporated into these ribosomal cores and restored their translational activity. Mutants lacking any part of the COOH-terminal region could be incorporated into these cores, as proven by two-dimensional polyacrylamide gels of the reconstituted particles. Mutant SsoL12 MC2 (residue 1-70) was sufficient for dimerization and incorporation into ribosomes. In contrast to the COOH terminally truncated mutants, L12 proteins lacking the 12 highly conserved NH2-terminal residues or the entire NH2-terminal region (44 amino acids) are unable to bind to ribosomes, suggesting that the SsoL12 protein binds with its NH2-terminal portion to the ribosome. None of the mutants could significantly increase the translational activity of the core particles suggesting that every deleted part of the protein was needed directly or indirectly for translational activity. Our results suggest that the COOH terminally truncated mutants were bound to ribosomes but not functional for translation. Cores preincubated with these COOH terminally truncated mutants regained activity when a second incubation with the entire overexpressed SsoL12e protein followed. This finding suggests that archaebacterial L12 proteins are freely exchanged on the ribosome.

Summary We have sequenced a gene in the archaebacterium Sulfolobus solfataricus that codes for a protein that shows sequence similarity to the alpha subunit of the signal recognition particle receptor or docking protein In eukaryotes and the product of the ftsY gene in Escherichia coli. Comparison of the Sulfolobus‘docking protein’ with its eukaryotic and eubacterial counterparts showed that the region of highest sequence similarity corresponds to a GTP-binding site. The presence of this gene in archaebacteria suggests that some of the components involved in protein transport have been conserved in the three kingdoms.

The gene for the ribosomal protein L5 from the archaebacterium Sulfolobus acidocaldarius has been isolated and sequenced. The gene codes for a basic protein of molecular weight 29 165 Da. This protein shows substantial similarity to the equivalent protein from other archaebacteria as well as from yeast, and considerably less similarity to the equivalent eubacterial protein. These results support the concept of the archaebacteria as a monophyletic kingdom more closely related to eukaryotes than to eubacteria.

Two-dimensional electrophoresis of total protein from 50 S ribosomal subunits of the archaebacterium Sulfolobus solfataricus demonstrated a complex between two proteins that was stable in 6 M urea, but dissociable in detergent or below pH 5.5. The proteins, numbered L1 and L10 according to their electrophoretic mobilities, corresponded to Escherichia coli ribosomal proteins L10 and L7/L12, respectively. The members of the complex were therefore designated Sso L10e and Sso L12e. Sso L12e had other properties in common with E. coli L7/L12: low molecular weight, relative acidity, selective release from the ribosome by high salt/ethanol, and dimeric structure. The Sso L12e.Sso L10e complex was isolated by gel filtration of total 50 S proteins in 4 M urea. The stoichiometry of the components was approximately four copies of Sso L12e to one copy of Sso L10e. The occurrence in an archaebacterium of a complex of acidic ribosomal proteins similar to E. coli (L7/L12)4.L10 and eukaryotic (P1)2/(P2)/.P0 strongly supports the concept that this element of quaternary structure is a major conserved feature of the ribosome and reaffirms its importance in the translocation step of protein synthesis.

We report UBVRI observations of the optical afterglow of the gamma-ray burst GRB 021004. We observed significant (10-20%) deviations from a power law decay on several time scales, ranging from a few hours down to 20-30 minutes. We also observed a significant color change starting ~1.5 days after the burst, confirming the spectroscopic results already reported by Matheson et al. (2002). We discuss these results in the context of several models that have recently been proposed to account for the anomalous photometric behavior of this event., Comment: Submitted to ApJL, 14 pages, 4 figures. Data available on anonymous ftp at ftp://cfa-ftp.harvard.edu/pub/kstanek/GRB021004

Relatively little is still known about the sense of taste, or contact chemoreception, compared with other sensory modalities, despite its importance to many aspects of animal behaviour. The central projections of the sensory neurons from bimodal contact chemoreceptors (basiconic sensilla) were compared with those from mechanosensory tactile hairs located on similar regions of the middle leg of the locust. Basiconic sensilla are multiply innervated, containing one mechanosensory and several chemosensory neurons, whereas tactile hairs are innervated by a single mechanosensory neuron. We show that the sensory neurons from tactile hairs form a complete 3-dimensional somatotopic map in the mesothoracic ganglion. Sensory neurons from hairs located on the coxa projected to a region near the midline of the ganglion with neurons from hairs located on progressively more distal parts of the leg arborizing in successively more lateral regions of neuropil. All the neurons from basiconic sensilla, both mechanosensory and chemosensory, also projected in a similar, strictly somatotopic, manner, and the arbors from these neurons overlapped considerably with those from tactile hairs on equivalent parts of the leg to form a continuous region. Thus, the position of a receptor on the leg is preserved in the central nervous system not only for the mechanosensory neurons from both tactile hairs and basiconic sensilla but also for chemosensory neurons. We could observe no anatomical features or small differences in projection region between sensory neurons from individual basiconic sensilla consistent with differences in modality.

The genes for nine ribosomal proteins, L24, L5, S14, S8, L6, L18, S5, L30, and L15, have been isolated and sequenced from the spc operon in the archaeon (Crenarchaeota) Sulfolobus acidocaldarius, and the putative amino acid sequence of the proteins coded by these genes has been determined. In addition, three other genes in the spc operon, coding for ribosomal proteins S4E, L32E, and L19E (equivalent to rat ribosomal proteins S4, L32, and L19), were sequenced and the structure of the putative proteins was determined. The order of the ribosomal protein genes in the spc operon of the Crenarchaeota kingdom of Archaea is identical to that present in the Euryarchaeota kingdom of Archaea and also identical to that found in bacteria, except for the genes for r-proteins S4E, L32E, and L19E, which are absent in bacteria. Although AUG is the initiation codon in most of the spc genes, GUG (val) and UUG (leu) are also used as initiation codons in S. acidocaldarius. Over 70% of the codons in the Sulfolobus spc operon have A or U in the third position, reflecting the low GC content of Sulfolobus DNA. Phylogenetic analysis indicated that the archaeal r-proteins are a sister group of their eucaryotic counterparts but did not resolve the question of whether the Archaea is monophyletic, as suggested by the L6P, L15P, and L18P trees, or the question of whether the Crenarchaeota is separate from the Euryarchaeota and closer to the Eucarya, as suggested by the S8P, S5P, and L24P trees. In the case of the three Sulfolobus r-proteins that do not have a counterpart in the bacterial ribosome (S4E, L32E, and L19E), the archaeal r-proteins showed substantial identity to their eucaryotic equivalents, but in all cases the archaeal proteins formed a separate group from the eucaryotic proteins.

A series of mutant L12 ribosomal proteins was prepared by site-directed mutations in the L12 protein gene of the archaeon Sulfolobus acidocaldarius. The mutant protein genes were overexpressed in Escherichia coli, and the products purified and incorporated into ribosomal cores which had been ethanol extracted to remove wild-type L12 protein. Measurements were made to determine if the mutation affected the binding of the L12 protein to the ribosome core or affected the translational activity of the resulting ribosome. Changing tyrosine [3] or tyrosine [5], conserved in all archaea and present in all eukarya in positions [3] and [7], to phenylalanine had no effect on binding or translational activity while changes to glycine significantly reduced binding and translational activity. Changing the single arginine [37] residue, conserved in almost all archaeal and eukaryal L12 proteins, to lysine, glutamic acid, glutamine, or glycine had no effect on binding to the core and had little or no significant effect on translational activity. The same was true when lysine [39], conserved in all archaeal L12 proteins, was changed to arginine, glutamic acid, glutamine, or glycine. Changing phenylalanine [104], the penultimate amino acid at the C-terminal end, which is conserved in all archaeal and eukaryal L12 proteins, to tyrosine or glycine had no effect on binding but lowered the translational activity by 60 and 75%, respectively, suggesting that this amino acid plays an important role in translation. Deletion of the highly charged region in the C-terminal domain, which is present in all archaeal and eukaryal L12 proteins, decreased transitional activity by 50%, suggesting this region is also involved in factor interactions.

We present the results of an intensive ground-based spectrophotometric monitoring campaign of the Seyfert galaxy NGC~4151 for a period of over two months, with a typical temporal resolution of one day. Light curves for four optical continuum bands and the H$\alpha$ and H$\beta$ emission lines are given. During the monitoring period, the continuum at 6925~\AA\ varied by $\sim$17\% while the continuum at 4600~\AA\ varied by $\sim$35\%, with larger variations in the near UV. The wavelength dependence of the variation amplitude also extends into the far UV. The dependence in the 2700$-$7200~\AA\ range can be explained by the different relative starlight contributions at different wavelengths, but the large variability at 1275~\AA\ cannot be explained in this way. The continuum variability timescale is of order 13 days and is similar at all optical wavelength bands. No evidence for a time lag between the optical continuum and the UV continuum and emission lines was found. The H$\alpha$ emission line flux varied by about 12\% with a gradual rise throughout the campaign. Its cross correlation with the continuum light curve gives a lag of $0-2$ days. The variations in the H$\beta$ emission line flux are about 30\% and lag the continuum by 0$-$3 days. This is in contrast to past results where a time lag of 9$\pm$2 days was found for both emission lines. This may be due to a different variability timescale of the {\em{ionizing}} continuum, or to a real change in the BLR gas distribution in the 5.5 years interval between the two campaigns., Comment: 16 pages, LaTeX (including aas2pp4 and epsf), including 10 PostScript figures; To appear in the ApJ (October 20, 1996) Vol. 470

A common finding in both vertebrates and invertebrates is that the central terminals of their mechanosensory neurones receive synaptic inputs. These inputs are often caused by neurones that release GABA, and change the chloride conductance which, at the normal resting potential, causes a depolarisation. These inputs in turn reduce the efficacy with which the sensory spikes release transmitter onto postsynaptic neurones. The consequence of this presynaptic inhibition is that the information coded in the spikes of the sensory neurones may not be reliably transmitted to postsynaptic neurones. This paper suggests a new function for some of these presynaptic inputs, from an analysis of proprioceptive afferents in a locust. It proposes that they can form part of an automatic gain control mechanism that limits the efficacy of the proprioceptive signals, when activated by the spikes in other afferents from the same sense organ responding to the same movement. The result is that the actions of one sensory neurone are interpreted by the central nervous system only in the context of the network actions of all the other sensory neurones responding to the same stimulus.

We have cloned and sequenced four ribosomal protein genes from the extreme thermophilic archaeon Sulfolobus acidocaldarius P1. These genes code for proteins equivalent to L11, L1, L10 and L12 from Escherichia coli. The genes for the Sulfolobus L11, L1, L10 and L12 proteins are arranged in the same order as the equivalent genes in E. coli, i.e. L11-L1-L10-L12, and are transcribed as a single unit. Sequences resembling the consensus sequence for archaeal promoters have been detected upstream of the transcription initiation site. Transcription ends at several sites following a pyrimidine-rich region. The genes for proteins L11, L10 and L1 start with unusual initiation codons: GUG in the case of the L1 and L10 genes; and UUG in the case of L11. There are overlapping stop/start codons between the L11 and L1 genes, and between the L1 and L10, suggesting that the translation of the four genes might be coupled as in the bacteria.

The sequences of two ribosomal proteins from two widely divergent species of archaebacteria, Halobacterium cutirubrum and Sulfolobus solfataricus, have been deduced from the structure of their respective genes. These two proteins were found to be equivalent to the L11 and L1 ribosomal proteins of the eubacterium Escherichia coli. Sequence comparison revealed that the archaebacterial L11e (equivalent to E. coli L11) proteins are longer than the eubacterial protein due to a C-terminal extension of about 30 residues. The archaebacterial L11e proteins, like the E. coli L11, are rich in proline residues; most of these are conserved. L11 is the most highly methylated protein in the E. coli ribosome. However, sites of methylation are generally not conserved in the archaebacterial L11e proteins. The region of highest sequence similarity between L11 and the archaebacterial L11e proteins is the N-terminal domain. This domain is believed to interact with release factor 1 during termination of translation. The amino acid sequences of the archaebacterial L1e proteins were compared to the eubacterial E. coli L1 and Bacillus stearothermophilus L1e sequences. The archaebacterial L1e proteins are slightly shorter at both their N- and C-termini. A region of high sequence similarity (7 of 14 residues) occurs near the center of the proteins.

We present the data and initial results from a combined Hubble Space Telescope (HST)/IUE/ground-based spectroscopic monitoring campaign on the Seyfert 1 galaxy NGC 5548 that was undertaken in order to address questions that require both higher temporal resolution and higher signal-to-noise ratios than were obtained in our previous multiwavelength monitoring of this galaxy in 1988-1989. IUE spectra were obtained once every 2 days for a period of 74 days beginning on 1993 March 14. During the last 39 days of this campaign, spectroscopic observations were also made with the HST Faint Object Spectrograph (FOS) on a daily basis. Ground-based observations, consisting of 165 optical spectra and 77 photometric observations (both CCD imaging and aperture photometry), are reported for the period 1992 October-1993 September, although many of the data are concentrated around the time of the satellite-based program. These data constitute a fifth year of intensive optical monitoring of this galaxy. In this contribution we describe the acquisition and reduction of all of the satellite and ground-based data obtained in this program. We describe in detail various photometric problems with the FOS and explain how we identified and corrected for various anomalies.

We present ground-based data of the BL Lac object PKS 2155-305 obtained during a large international campaign spanning the electro–magnetic spectrum from the radio waves to X-rays in November 1991. For the complete description of the observations and data analysis we refer to the paper by Courvoisier et al. 1993, and references therein. The ground-based data include radio, infrared JHKL and UBVRI fluxes as well as optical and near IR polarimetry.The broad-band optical and near IR data from U to I exhibit the same behaviour in all bands: the flux nearly doubled over the well-covered period of 23 days. The cross-correlation function does not reveal any significant changes in the light-curves. Though significant variations in 24 hours have been recorded, the cumulated Fourier power spectrum drops to the noise level for periods shorter than 2.5 days. The spectral index remained constant.The polarised flux varied by a larger factor than the total flux and did not follow the same pattern. The degree of polarisation and polarisation angle are nearly independent of the wavelength and are strongly correlated in all filters.In the radio domain the spectral index increased from −0.1 on November 5 to +0.02 on 25-th.The absence of the lag between the optical and infrared bands and the polarisation variations are consistent with a model in which the variability is caused by micro-lensing of the source (Stickel, Fried and Kühr 1988). One would, however, expect in this model that the variation in the polarisation and the total flux are tightly correlated contrary to what is observed.The constant shape of the continuum spectral energy suggests that only the number of electrons whose emission is beamed towards the observer changes, rather than the arrival of fresh electrons that are being accelerated.The variability of the polarisation may be explained by changes in the geometry of the magnetic field (dominant direction). This is consistent with the observed variations of the polarisation angle.

The intracellular potassium concentration and percentage of acidic ribosomal proteins were determined for nine methanogenic bacteria representing diverse phylogenetic groupings. Representatives of the Methanobacteriaceae family possessed very high internal potassium concentrations: Methanobrevibacter arboriphilus, 1225 mM; Methanobrevibacter smithii, 1065 mM; Methanobacterium thermoautotrophicum, 1103 mM; Methanobacterium bryantii, 861 mM; and Methanobacterium strain G2R, 886 mM. Members of other families tested maintained much lower internal concentrations of potassium. Methanosarcina barkeri (family Methanosarcinaceae) and Methanospirillum hungatei (family Methanomicrobiaceae) maintained approximately 200 mM internal potassium, while Methanococcus voltae (family Methanococcaceae) possessed an intermediate concentration of 725 mM. Those organisms maintaining the highest internal potassium concentrations also had the largest number of acidic ribosomal proteins. There appeared to be a correlation among the phylogenetic placement of the organism (based on 16S rRNA sequence data), its content of intracellular potassium, and the percentage of acidic ribosomal proteins. Those methanogens most closely related to extreme halophiles possessed the highest concentrations of internal potassium and had an increased percentage of acidic ribosomal proteins, both properties of halophilic bacteria.

The genes corresponding to the L10 and L12 equivalent ribosomal proteins (L10e and L12e) ofEscherichia coli have been cloned and sequenced from two widely divergent species of archaebacteria,Halobacterium cutirubrum andSulfolobus solfataricus. The deduced amino acid sequences of the L10e and L12e proteins have been compared to each other and to available eubacterial and eucaryotic sequences. We have identified the hyman P0 protein as the eucaryotic L10e. The L10e proteins from the three kingdoms were found to be colinear. The eubacterial L10e protein is much shorter than the archaebacterial-eucaryotic proteins because of two large deletions, one internal and one at the carboxy terminus. The archaebacterial and eucaryotic L12e proteins were also colinear; the eubacterial protein is homologous to the archaebacterial and eucaryotic L12e proteins, but has suffered rearrangement through what appear to be gene fusion events. Intraspecies comparisons between L10e and L12e sequences indicate the archaebacterial and eucaryotic L10e proteins contain a partial copy of the L12e protein fused to their carboxy terminus. In the eubacteria most of this fusion has been removed by the carboxy terminal deletion. Within the L12e-derived region, a 26-amino acid-long internal modular sequence reiterated thrice in the archaebacterial L10e, twice in the eucaryotic L10e, and once in the eubacterial L10e was discovered. This modular sequence also appears to be present as a single copy in all L12e proteins and may play a role in L12e dimerization, L10e–L12e complex formation, and the function of L10e–L12e complex in translation. From these sequence comparisons a model depicting the evolutionary progression of the L10e and L12e genes and proteins from the primordial state to the contemporary archaebacterial, eucaryotic, and eubacterial states is presented.

The nucleotide sequence of ribosomal 5 S RNA from a halophilic bacterium, Halobacterium cutirubrum, grown in 4 M sodium chloride is U-U-A-A-G-G-C-G-G-C-C-A-U-A-G-C-G-G-U-G-G-G-G-U-U-A-C-U-C-C-C-G-U-A-C-C-C-A-U-C-C-C-G-A-A-C-A-C-G-G-A-A-G-A-U-A-A-G-C-C-C-G-C-C-U-G-C-G-U-U-C-C-G-G-U-C-A-G-U-A-C-U-G-G-A-G-U-G-C-G-A-G-C-C-U-C-U-G-G-G-A-A-A-U-C-C-G-G-U-U-C-G-C-C-G-C-C-U-A-C-U. This nucleotide sequence is the longest prokaryotic 5 S rRNA to be reported and unlike other 5 S species does not contain a terminal mononucleoside diphosphate residue at its 5'-end. When compared to other 5 S rRNA's, the sequence homology is greatest (about 68%) with Bacillus subtilis; there is a lower but similar degree of homology (about 58%) with either Escherichia coli or human 5 S RNA. The comparisons further indicate that among 5 S RNA's, eleven of the nucleotide residues are unique to H. cutirubrum. Estimates of the secondary structure of the H. cutirubrum 5 S RNA molecule contain one additional stable hairpin loop which is not found in other 5 S rRNA species; this unusual structure is probably an adaptation to the high salt environment within H. cutirubrum cells.

The gastrointestinal absorption of vitamin D3 and its biotransformation to 25-hydroxycholecalciferol was studied in patients with drug-induced osteomalacia. The mean coefficient of absorption was virtually identical in the drug-treated group (82.8%) and the control (83.8%). The biotransformation of vitamin D3 to 25-hydroxycholecalciferol was significantly accelerated (P less than 0.03) in the drug-treated group compared to the control group. These data suggest that vitamin D absorption is not significantly altered but that biotransformation of vitamin D3 to 25-hydroxycholecalciferol is accelerated in drug-induced osteomalacia.

The nucleotide sequence of ribosomal 5 S RNA from Thermus aquaticus grown at 75 degrees is p(A)-A-U-C-C-C-C-G-C-C-C-U-U-A-G-C-G-G-C-G-U-G-G-A-A-C-A-C-C-C-G-U-U-C-C-C-A-U-U-C-C-G-A-A-C-A-C-G-G-A-A-G-U-G-A-A-A-C-G-C-G-C-C-A-G-C-G-C-C-G-A-U-G-G-U-C-A-C-U-G-G-G-A-C-C-G-C-A-G-G-G-U-C-C-U-G-G-A-G-A-G-U-A-G-G-U-G-C-U-G-G-U-G-C-G-G-G-G-A-(U). The major molecular species is 120 nucleotides long; some molecules are one or two nucleotides shorter with one less nucleotide at either or both termini. When compared to other 5 S rRNAs, the sequence homology was greater with a thermophile bacterium (Bacillus stearothermophilus) than with mesophilic species. The comparisons further indicate that among prokaryotes, eleven of the nucleotide residues in T. aquaticus 5 S RNA may be largely restricted to thermophiles. Possible models for the secondary structure of T. aquaticus 5 S rRNA are discussed with respect to products of limited digestion and the unique nucleotides.

Summary When the primary structure of the ribosomal ‘A’ protein from Halobacterium cutirubrum, Methanobacterium thermoautotrophicum and Sulfolobus acidocaldarius are compared to each other and to the equivalent protein in eubacteria and eukaryotes the data obtained do not support the widely accepted concept of a deep division within the archaebacteria consisting of the sulfur-dependent bacteria in one subgroup and the methanogens/extreme halophiles in the other. If a division were to be made based on the ribosomal protein data it would have the extreme halophiles separate from the methanogens/sulfur-dependent bacteria. The data also indicate the ‘A’ protein from the extreme halophile shows much more structural similarity to the equivalent eubacterial protein than does the ‘A’ protein from the Mb. thermoautotrophicum and S. acidocaldarius. In turn, the Sulfolobus ‘A’ protein shows certain structural features very similar to those shown by the equivalent eukaryotic protein.

The 50-S ribosomal subunits from the extreme halophilic bacterium, Halo-bacterium cutirubrum, stable structurally and functionally in concentrated salt solutions were subjected to ionic environments depleted in either K+ or Mg2+ or both. Under these conditions specific classes of proteins are released from the subunit along with the 5 S RNA. Two-dimensional electrophoretic analysis of the resultant split protein fractions indicate some mutually exclusive effects of specific ions on the binding of specific proteins to the 23 S RNA as well as on the retention of 5 S RNA within the ribosomal macrostructure.

Ribosomal small subunits are organized in three general structural patterns that correspond to the eubacterial, archaebacterial, and eukaryotic lineages. Within each of these lineages, ribosomal structure is highly conserved. Small subunits from all three lineages share a common overall structure except for the following differences: (i) small subunits from archaebacteria and from the cytoplasmic component of eukaryotes both contain a feature on the head of the subunit, the archaebacterial bill, that is absent in eubacteria, and (ii) eukaryotic small subunits contain additional regions of density at the base of the subunit, the eukaryotic lobes, that are absent in archaebacteria and in eubacteria. We interpret the intralineage conservation of ribosomal three-dimensional structure as forming a phylogenetic basis for regarding archaebacteria, eubacteria, and eukaryotes as primitive lines. Although our data are separate and independent from those of Woese and Fox, they lend further support to their proposal [Woese, C. R. & Fox, G. E. (1977) Proc. Natl. Acad. Sci. USA 74, 5088-5090]. These data also provide a simple, rapid, and accurate method for classifying organisms and for identifying new lineages. Finally, interlineage variation of ribosomal structure is used to establish a rigorous framework for considering the evolution of these three lines.

The ribosomal A protein (SacL12) from the archaebacterium Sulfolobus acidocaldarius has been sequenced. The protein contains 105 amio acids, has a composition of Asp2, Asn3, Thr4, Ser6, Glu17, Gln4, Pro3, Gly7, Ala18, Val7, Met2, Ile7, Leu9, Tyr2, Phe1, His1, Lys11, Arg1, and a molecular mass of 11 126 Da. The Sulfolobus protein shows many features in common with the equivalent proteins in the eukaryotes such as 35–40% sequence homology and similar hydrophilicity profiles, features much less evident when this protein is compared to eubacterial L12 proteins. SacL12 contains an unusual sequence of alternating clusters of lysine and glutamic acid (—EKKEEKKEEEKK—) in the C-terminal region. Similar sequences are found in some eukaryotic L12 proteins.

Physical studies on the effect of temperature and ionic conditions on the secondary, tertiary, and quaternary structure of the ribosomal "A" protein, equivalent to L7/L12 in Escherichia coli, from two archaebacteria were performed using circular dichroism and sedimentation equilibrium measurements. The two archaebacteria investigated were Halobacterium cutirubrum, an extreme halophile, and Methanobacterium thermoautotrophicum, a thermophile which also showed properties of a moderate halophile. The changes in the secondary structure and the thermostability of these proteins were directly related to the internal salt concentrations of the two archaebacteria. At the higher salt concentrations the changes in the secondary structure resulted in changes in the tertiary and quaternary structure of these proteins.

When lysozyme–EDTA spheroplasts are formed from Escherichia coli cells, only a small fraction of the total peptidase activity of the cell is released into the supernatant fluid under conditions where ribonuclease is quantitatively released. Purification of the released peptidase on DEAE-Sephadex gives two fractions. The peptidase in one fraction shows the same substrate specificity, metal ion requirements, and chromatographic properties as the ribosomal peptidase of the cell; the peptidase in the other fraction shows the same properties as the soluble peptidases of the cell. The ribosomal peptidase does not belong to the group of hydrolytic enzymes that are released when E. coli cells are converted into spheroplasts.

Properties of a peptidase present in E. coli ribosomes have been studied. The enzyme is tightly bound to the ribosomes, as indicated by repeated washings and centrifugations, sucrose density gradient centrifugations, and electrophoresis on cellulose acetate. The level of enzyme activity in the 30 S particles is twice that found in the 50 S particles. When the ribosome structure is disrupted by enzymic or chemical means, the peptidase behaves similarly to the bulk of the ribosomal protein.

A modified Yemm and Cocking ninhydrin–cyanide reagent has been developed which gives quantitative color yields with free amino acids, but much lower yields with most peptides tested. Using this reagent, a more sensitive assay for peptidase activity has been developed, and its use in column fractionation of peptidase activity is described.The ϵ values for peptides, obtained with the modified reagent, are compared to those obtained with the conventional ninhydrin–hydrindantin reagent. The formation of Ruhmann's Purple by the modified reagent is inhibited by Tris buffer. No inhibition occurs with the ninhydrin–hydrandantin reagent. The absorption spectra of the two reaction mixtures indicate that Tris reacts in a different manner with the two reagents.

The ribosomes of Myxobacter 495 are similar to other bacterial ribosomes in that the 70 S monomer is made up of a 50 S subunit (containing 23 S and 5 S RNA) and a 30 S subunit (containing 16 S RNA). The base composition of the ribosomal RNA is very similar to that of E. coli. The Myxobacter 495 ribosomes contain nucleases that are not removed by washing with 1 M (NH4)2SO4 and which are relatively insensitive to inhibition by Macaloid or sodium dodecyl sulfate. Only in the presence of diethyl pyrocarbonate was it possible to isolate intact 16 S and 23 S RNA. The (NH4)2SO4-washed ribosomes were much less stable than the unwashed ribosomes due apparently to activation of a nuclease which was located mainly in the 30 S subunit.

The basic aminopeptidase activity was found in both the 30 S and 50 S ribosomal subunit of Escherichia coli B; the specific activity of the enzyme in the 30 S particle was about six times that found in the 50 S particle. Although about 50% of the enzyme was released from E. coli B ribosomes on dissociation into the subunits, this was not observed with E. coli Q-13, a ribonuclease I-less strain. The partition of the basic aminopeptidase activity between the soluble and ribosomal fractions (isolated in 60 mM KCl) of E. coli was determined by the strain of E. coli used, as well as the stage and temperature of growth. Under similar growth conditions, a significantly greater amount of enzyme was found in the ribosomal fraction of E. coli B than in the corresponding fraction of E. coli K-12. When E. coli B cells were disrupted in 300 mM KCl, over 90% of the enzyme was found in the soluble fraction. The remaining 10% on the ribosomal particle had enriched activity towards methionyl peptides suggesting that more than one enzyme is present in the basic aminopeptidase fraction.

Ribonucleoprotein sub-particles from the 30-S ribosomal subunits of Halobacterium cutirubrum, Escherichia coli and Bacillus stearothermophilus have been prepared by exposing the ribosomal particles to 3.5 M LiCl in the presence of 0.01 M EDTA. The sub-particles formed contained only a few proteins. The two proteins present in the E. coli ribonucleoprotein subparticle were S8 and S15, both assembly proteins. When these ribonucleoprotein sub-particles were treated with ribonuclease (A or T 1 ) and then fractionated on Bio-Gel P-60, well defined fragments were obtained. In two of the Bio-Gel fractions (B and C) the fragments contained both RNA and protein and were stable in CsCl. The nucleotide composition of these two fractions showed an enriched C + G content. The four proteins found in the ribonucleoprotein sub-particle from B. stearothermophilus were present in either Bio-Gel fraction B or C, not in both, and their location was determined by the ribonuclease used to degrade the sub-particle. This would suggest the proteins are bound to specific sites on the ribonucleoprotein sub-particle.

1. When ribosomes from early log-phase cultures of Escherichia coli were incubated with 0.5 mM p -chloromercuribenzoate (PCMB) (in 10 mM Tris buffer (pH 7.6) containing 10 mM Mg 2+ ), the 100-S dimers were completely dissociated into 70-S monomers. 2. The dissociation was not reversed by increased concentrations of Mg 2+ and/or spermine. It was reversed, however, by 2-mercaptoethanol. 3. Mild I 2 oxidation also resulted in 100-S dissociation. Other sulfhydryl reagents, N -ethylmaleimide, 5,5′-dithio-bis-(2-nitrobenzoic acid) and iodacetate, showed no effect. 4. Approximately 10 moles of PCMB were bound per ribosome prior to the onset of dissociation of the 100-S particles. When 20–25 PCMB molecules were bound per ribosome dissociation was almost complete. 5. Dissociation of 100-S ribosomes stems from the reaction of PCMB with sulfhydryl groups presumably in the ribosomal protein. 6. Incubation of untreated ribosomes with 2-mercaptoethanol resulted in an association of 70-S particles into the 100-S dimer, suggesting the relative concentration of the 100- and 70-S particles in vivo may be governed by sulfhydryl interactions.

Peptidase-rich fractions were prepared from autolyzed extracts of pig kidney. These preparations showed many properties in common with leucine aminopeptidase but exhibited remarkable stability when subjected to vigorous emulsification with chloroform–octanol. By chromatography on DEAE-cellulose and on Sephadex gel under appropriate conditions, it was demonstrated that the aminopeptidase in these preparations exists in a conjugated form which is dissociable into an enzymatically-active protein moiety and inactive fractions containing nucleic acid. The dissociated form of the enzyme is extremely labile and shows an A[280/260] ratio of 1.2. Starch gel electrophoresis of the purified enzyme fraction shows several enzymatically-active protein bands and only traces of inactive protein. Preliminary evidence suggests that the aminopeptidase present in the supernatant fraction of non-autolyzed homogenates of kidney tissue exists also in a protected conjugated form.