Low-Temperature and High-Pressure <i>p</i>–ρ–<i>T</i> Relation for 1‑(2-Methoxyethyl)-1-methylpyrrolidinium Bis(trifluoromethylsulfonyl)imide and 1‑C_<i>n</i>‑3-methylimidazolium Thiocyanate with <i>n</i> = 2 and 4

Experimental <i>p</i>–ρ–<i>T</i> data are reported for 1-(2-methoxyethyl)-1-methylpyrrolidinium bis­(trifluoromethylsulfonyl)­imide ([MOEMPYR]­[NTf₂]), and two ionic liquids with thiocyanate ([SCN]) anion and 1-C_<i>n</i>-3-methylimidazolium ([C_<i>n</i>MIM]) cation with <i>n</i> = 2 and 4, which are still poorly studied in this respect. The data were obtained by using (i) a constant volume apparatus at temperatures from (218 to 353) K at nominal pressures of 1 MPa and from (10 to 50) MPa with a 10 MPa step, and (ii) tensiometer Krüss using buoyancy method at the pressure of 0.1 MPa and at temperatures from (262 to 365) K. Thus, the temperature and pressure region covered with experimental <i>p</i>–ρ–<i>T</i> data has been substantially extended to lower temperatures for [C₄MIM]­[SCN] and [MOEMPYR]­[NTf₂] and to higher pressures for [C₂MIM]­[SCN] and [C₄MIM]­[SCN]. The expanded combined uncertainty at the 0.95 confidence level of the reported isochoric densities takes its maximum value at the lower end of the temperature interval of the data, namely, from 1.2 kg·m^–3 for [C₂MIM]­[SCN] to 1.7 kg·m^–3 for [MOEMPYR]­[NTf₂], which is about 1.0·10^–3 ρ. The global topology of the liquid-state region in the internal pressure-specific volume plane is determined by presence or absence of the hydrogen bonding in the liquid

Low Temperature Densities from (218 to 364) K and up to 50 MPa in Pressure and Surface Tension for Trihexyl(tetradecyl)phosphonium Bis(trifluoromethylsulfonyl)imide and Dicyanamide and 1‑Hexyl-3-methylimidazolium Hexafluorophosphate

Experimental <i>p</i>-ρ-<i>T</i> data obtained with a constant volume apparatus are reported for two ionic liquids with trihexyl­(tetradecyl)­phosphonium ([THTDP]) cation and bis­(trifluoromethylsulfonyl)­imide, [NTf₂], and dicyanamide, [DCA], anion and for 1-hexyl-3-methylimidazolium hexafluorophosphate, [C₆MIM]­[PF₆]. The measurements were conducted at temperatures from (218 to 364) K and at nominal pressures of 1 MPa and from (10 to 50) MPa with a 10 MPa step. Thus, the temperature region covered with experimental <i>p</i>-ρ-<i>T</i> data has been substantially extended to lower temperatures for all three substances. The expanded combined uncertainty at the 0.95 confidence level of the reported densities takes its maximum value at the lower end of the temperature interval of the data, namely 1.3 kg·m^–3 (1.3·10^–3ρ) for [THTDP]­[NTf₂], 0.6 kg·m^–3 (0.7·10^–3ρ) for [THTDP]­[DCA], and 1.8 kg·m^–3 (1.4·10^–3ρ) for [C₆MIM]­[PF₆]. The studied ionic liquids show a specific type of the temperature and pressure dependence of their internal pressure, different from that of molecular liquids such as water or aliphatic alcohols. In addition, experimental 0.1 MPa density data and air–liquid surface tension data are reported for both phosphonium based ionic liquids obtained with the buoyancy method and the Wilhelmy plate method, respectively, at temperatures from (263 to 365) K

<i>P</i>–ρ–<i>T</i> Measurements for 1-Alkyl-3-methylimidazolium-Based Ionic Liquids with Tetrafluoroborate and a Trifluoromethanesulfonate Anion

The present paper reports results of density measurements for 1-C_<i>n</i>-3-methylimidazolium-based tetrafluoroborates and trifluoromethanesulfonates with <i>n</i> = 2 and 4 and with <i>n</i> = 2, 4, and 6, respectively. For the tetrafluoroborates, the measurements were performed at temperatures from (285 and 220) K, respectively, to approximately 357 K. For the trifluoromethanesulfonates, the measurements were conducted at temperatures from 353 K down to the melting temperature of the substance. Data at nominal pressures of 1 MPa and from (10 to 60) MPa with a 10 MPa step were obtained. An isochoric apparatus was used, making possible density measurements at temperatures below 273.15 K. The combined uncertainty at the 95 % confidence level in the resultant density data due to the measuring procedure is estimated to be 1 kg·m^–3, that is, about 0.1 % relative to the density value. Results of a quantitative analysis are reported of the effect of water and chloride anion impurities present in the sample on the density of the ionic liquids of interest. The sodium cation was studied experimentally as a candidate for the impurity causing an increase in ionic liquid density. At the same mass fraction, the sodium cation proves to be four times more effective than the chloride anion in changing the density of [HMIM]­[BF₄]

<i>P</i>–ρ–<i>T</i> Measurements for 1-Ethyl and 1-Butyl-3-methylimidazolium Dicyanamides from Their Melting Temperature to 353 K and up to 60 MPa in Pressure

New experimental data on the density of two 1-alkyl-3-methylimidazolium based dicyanamides ([C_<i>n</i>-MIM] [N­(CN)₂], <i>n</i> = 2 and 4) are reported, obtained with a constant volume apparatus, which makes possible density measurements at subzero temperatures. The measurements were conducted at temperatures from 350 K down to the melting temperature of the substance and at nominal pressures of 1 MPa and from (10 to 60) MPa with a 10 MPa step. The combined uncertainty at the 0.95 confidence level of the resultant density data is estimated to be less than 1 kg·m^–3, that is, 0.1 % relative to the density value. A group contribution model of the <i>p</i>–ρ–<i>T</i> relation based on a large amount of data by different authors for 1-C_<i>n</i>-3-methylimidazolium-based ionic liquids with <i>n</i> = 2, 4, and 6 and with the [BF₄], [CF₃SO₃], and [N­(CN)₂] anions describes the dependence of density, isobaric expansivity, and isothermal compressibility on temperature, pressure, the length of the alkyl side chain of the cation, and the anion. This makes it possible to obtain the most reliable values of the density and to assess which sets of data can be considered as more certain than others

Generation of Recommendable Values for the Surface Tension of Water Using a Nonparametric Regression

Recommended values for the surface tension of water are presented, generated based on all the experimental data available from literature using nonparametric regression. A procedure was used which consists of neither a single data selection nor a determination of a single correlation function. The procedure works without the need for uncertainties in the processed data and other factors that characterize the experimental data credibility, while the processed collection of data sets only needs to be sufficiently large. The equation γ = <i>aτ</i>^<i>c</i>(1 – <i>bτ</i>) with <i>a</i> = 233.58 mN·m^–1, <i>b</i> = 0.61594, <i>c</i> = 1.2527, and τ = 1 – <i>T</i>/647.096 closely approximates the tabulated recommended surface tension values. New experimental data for air–liquid water interfacial tension are presented, measured at atmospheric pressure at 33 temperatures in the temperature range from 272.6 to 343.5 K. The measurements were performed by the Wilhelmy plate method using a Krűss K100Mk2 tensiometer. The uncertainty at 0.95 confidence level of the presented data is estimated to be 0.03 mN·m^–1 and their root-mean-square deviation from the recommended data is 0.027 mN·m^–1. The obtained results substantially extend the database of high-quality data for the air–liquid surface tension of water available from the literature. The worst-case error level of the proposed recommended values is estimated to be 0.1 mN·m^–1

Organization and Transcriptional Analysis of a Six-Gene Cluster around the rplK-rplA Operon of Corynebacterium glutamicum Encoding the Ribosomal Proteins L11 and L1

A cluster of six genes, tRNA(Trp)-secE-nusG-rplK-rplA-pkwR, was cloned and sequenced from a Corynebacterium glutamicum cosmid library and shown to be contiguous in the C. glutamicum genome. These genes encode a tryptophanyl tRNA, the protein translocase component SecE, the antiterminator protein NusG, and the ribosomal proteins L11 and L1 in addition to PkwR, a putative regulatory protein of the LacI-GalR family. S1 nuclease mapping analysis revealed that nusG and rplK are expressed as separate transcriptional units and rplK and rplA are cotranscribed as a single mRNA. A 19-nucleotide inverted repeat that appears to correspond to a transcriptional terminator was located in the 3′ region downstream from nusG. Northern analysis with different probes confirmed the S1 mapping results and showed that the secE-rplA four-gene region gives rise to four transcripts. secE was transcribed as a 0.5-kb monocistronic mRNA, nusG formed two transcripts of 1.4 and 1.0 kb from different initiation sites, and the two ribosomal protein genes rplK and rplA were cotranscribed as a single mRNA of 1.6 kb. A consensus L1 protein binding sequence was identified in the leader region of the rplK-rplA transcript, suggesting that expression of the rplK-rplA cluster was regulated by autogenous regulation exerted by the L1 protein at the translation level. The promoters of the nusG and rplK-rplA genes were subcloned in a novel corynebacterial promoter-probe vector and shown to confer strong expression of the reporter gene

Characterization of the Lacl-type transcriptional repressor RbsR controlling ribose transport in Corynebacterium glutamicum ATCC 13032

Nentwich SS, Brinkrolf K, Gaigalat L, et al. Characterization of the Lacl-type transcriptional repressor RbsR controlling ribose transport in Corynebacterium glutamicum ATCC 13032. MICROBIOLOGY. 2009;155(1):150-164.The gene products of the rbsRACBD(rbs) operon of C. glutamicum (cg1410-cg1414) encode a ribose-specific ATP-binding cassette (ABC) transport system and its corresponding regulatory protein (RbsR). Deletion of the structural genes rbsACBD prohibited ribose uptake. Deletion of the regulatory gene rbsR resulted in an increased mRNA level of the whole operon. Analysis of the promoter region of the rbs operon by electrophoretic mobility shift assays identified a catabolite-responsive element (cre)-like sequence as the RbsR-binding site. Additional RbsR-binding sites were identified in front of the recently characterized uriR operon (uriR-rbsK1-uriT-uriH) and the ribokinase gene rbsK2, In vitro, the repressor RbsR bound to its targets in the absence of an effector. A probable negative effector of RbsR in vivo is ribose 5-phosphate or a derivative thereof, since in a ribokinase (rbsK1 rbsK2) double mutant, no derepression of the rbs operon in the presence of ribose was observed. Analysis of the ribose stimulon in the C. glutamicum wildtype revealed transcriptional induction of the uriR and rbs operons as well as of the rbsK2 gene. The inconsistency between the existence of functional RbsR-binding sites upstream of the ribokinase genes, their transcriptional induction during growth on ribose, and the missing induction in the rbsR mutant suggested the involvement of a second transcriptional regulator. Simultaneous deletion of the regulatory genes rbsR and uriR finally demonstrated a transcriptional co-control of the rbs and uriR operons and the rbsK2 gene by both regulators, RbsR and UriR, which were furthermore shown to recognize the same cognate DNA sequences in the operators of their target genes

The LacI/GalR family transcriptional regulator UriR negatively controls uridine utilization of Corynebacterium glutamicum by binding to catabolite-responsive element (cre)-like sequences

Brinkrolf K, Ploeger S, Solle S, et al. The LacI/GalR family transcriptional regulator UriR negatively controls uridine utilization of Corynebacterium glutamicum by binding to catabolite-responsive element (cre)-like sequences. MICROBIOLOGY. 2008;154(4):1068-1081.The Cg1547 protein of Corynebacterium glutamicum ATCC 13032 is a member of the LacI/GalR family of DNA-binding transcriptional regulators. A defined deletion in the cg1547 gene, now designated uriR (uridine utilization regulator), resulted in the mutant strain C. glutamicum KB1547. Comparison of gene expression levels in C. glutamicum KB1547 and the wild-type strain revealed enhanced expression of the uriR operon genes cg1546 (ribokinase), cg1545 (uridine transporter) and cg1543 (uridine-pref erring nucleoside hydrolase). Gene expression of the uriR operon was stimulated by the presence of either uridine or ribose. Growth assays with C. glutamicum mutants showed that functional Cg 1543 and Cg 1545 proteins are essential for the utilization of uridine as the sole carbon source. Transcriptional regulation of the uriR operon is mediated by a 29 bp palindromic sequence composed of two catabolite-responsive element (cre)-like sequences and located in between the mapped -10 promoter region and the start codon of uriR. A similar cre sequence was detected in the upstream region of rbsK2 (cg2554), coding for a second ribokinase in C. glutamicum ATCC 13032. DNA band-shift assays with a streptavidin-tagged UriR protein and labelled oligonucleotides including the cre-like sequences of uriR and rbsK2 demonstrated the specific binding of the purified regulator in vitro. Whole-genome DNA microarray hybridizations comparing the gene expression in C. glutamicum KB1547 with that of the wild-type strain revealed that UriR is a pathway-specific repressor of genes involved in uridine utilization in C. glutamicum

Genetic makeup of the Corynebacterium glutamicum LexA regulon deduced from comparative transcriptomics and in vitro DNA band shift assays

Jochmann N, Kurze A-K, Czaja LF, et al. Genetic makeup of the Corynebacterium glutamicum LexA regulon deduced from comparative transcriptomics and in vitro DNA band shift assays. MICROBIOLOGY. 2009;155(5):1459-1477.The lexA gene of Corynebacterium glutamicum ATCC 13032 was deleted to create the mutant strain C. glutamicum NJ2114, which has an elongated cell morphology and an increased doubling time. To characterize the SOS regulon in C. glutamicum, the transcriptomes of NJ2114 and a DNA-damage-induced wild-type strain were compared with that of a wild-type control using DNA microarray hybridization. The expression data were combined with bioinformatic pattern searches for LexA binding sites, leading to the detection of 46 potential SOS boxes located upstream of differentially expressed transcription units. Binding of a hexahistidyl-tagged LexA protein to 40 double-stranded oligonucleotides containing the potential SOS boxes was demonstrated in vitro by DNA band shift assays. It turned out that LexA binds not only to SOS boxes in the promoter-operator region of upregulated genes, but also to SOS boxes detected upstream of downregulated genes. These results demonstrated that LexA controls directly the expression of at least 48 SOS genes organized in 36 transcription units. The deduced genes encode a variety of physiological functions, many of them involved in DNA repair and survival after DNA damage, but nearly half of them have hitherto unknown functions. Alignment of the LexA binding sites allowed the corynebacterial SOS box consensus sequence TcGAA(a/c)AnnTGTtCGA to be deduced. Furthermore, the common intergenic region of lexA and the differentially expressed divS-nrdR operon, encoding a cell division suppressor and a regulator of deoxyribonucleotide biosynthesis, was characterized in detail. Promoter mapping revealed differences in divS-nrdR expression during SOS response and normal growth conditions. One of the four LexA binding sites detected in the intergenic region is involved in regulating divS-nrdR transcription, whereas the other sites are apparently used for negative autoregulation of lexA expression