Short Carboxyl Research Articles

Acinetobacter nosocomialis utilizes a unique type VI secretion system to promote its survival in niches with prey bacteria.

Pathogenic bacteria of the Acinetobacter genus pose a severe threat to human health worldwide due to their strong adaptability, tolerance, and antibiotic resistance. Most isolates of these bacteria harbor a type VI secretion system (T6SS) that allows them to outcompete co-residing microorganisms, but whether this system is involved in acquiring nutrients from preys remains less studied. In this study, we found that Ab25, a clinical isolate of Acinetobacter nosocomialis, utilizes a T6SS to kill taxonomically diverse microorganisms, including bacteria and fungi. The T6SS of Ab25 is constitutively expressed, and among the three predicted effectors, T6e1, a member of the RHS effector family, contributes the most for its antimicrobial activity. T6e1 undergoes self-cleavage, and a short carboxyl fragment with nuclease activity is sufficient to kill target cells via T6SS injection. Interestingly, strain Ab25 encodes an orphan VgrG protein, which when overexpressed blocks the firing of its T6SS. In niches such as dry plastic surfaces, the T6SS promotes prey microorganism-dependent survival of Ab25. These results reveal that A. nosocomialis employs T6SSs that are highly diverse in their regulation and effector composition to gain a competitive advantage in environments with scarce nutrient supply and competing microbes.IMPORTANCEThe type VI secretion system (T6SS) plays an important role in bacterial adaptation to environmental challenges. Members of the Acinetobacter genus, particularly A. baumannii and A. nosocomialis, are notorious for their multidrug resistance and their ability to survive in harsh environments. In contrast to A. baumannii, whose T6SS has been well-studied, few research works have focused on A. nosocomialis. In this study, we found that an A. nosocomialis strain utilizes a contitutively active T6SS to kill diverse microorganisms, including bacteria and fungi. Although T6SS structural proteins of A. nosocomialis are similar to those of A. baumannii, the effector repertoire differs greatly. Interestingly, the T6SS of the A. nosocomialis strain codes for an ophan VgrG protein, which blocks the firing of the system when overexpressed, suggesting the existence of a new regulatory mechanism for the T6SS. Importantly, although the T6SS does not provide an advantage when the bacterium is grown in nutrient-rich medium, it allows A. nosocomialis to survive better in dry surfaces that contain co-existing bacteria. Our results suggest that killing of co-residing microorganisms may increase the effectiveness of strategies designed to reduce the fitness of Acinetobacter bacteria by targeting their T6SS.

The role of ring opening reaction chemistry of sultones/lactones in the direct zwitterionization of polyamide nano-filtration membranes

A facile one-step surface modification strategy was developed to zwitterionize polyamide based thin-film composite (PA-TFC) nanofiltration membranes via in-situ ring-opening reactions with a series of cyclic chemical reagents, including γ-butyrolactone(γ-BL), δ-valerolactone(δ-VL) and ε-caprolactone(ε-CL), 1,3-propanesultone (1,3-PS) and 1,4-butanesultone (1,4-BS). The impact of chemical reactivity, ring size, and length of formed zwitterionic chains of these modifiers on the surface properties and nanofiltration performance were comprehensively investigated. It was found that the loading density of the zwitterionic chains was mainly determined by internal ring strain of the cyclic modifying reagents, while the chemistry effect on water permeability was mainly reflected in the surface hydrophilic nature of the formed membranes. Loading of zwitterionic chains with medium length sulfonic acids tends to increase surface hydrophilicity and membrane water permeability while loading of short carboxylate zwitterionic chains tends to increase the retention selectivity of membranes. NF membranes with long and soft hydrophobic –C4H8- and –C5H10- hydrocarbon chains tend to have less flux and retention selectivity. Owing to these competing factors, the NF membranes modified by 1,4-BS exhibited the greatest water permeability (10.9 L/m2⋅h⋅bar) with high retention selectivity (MgCl2/NaCl ratio: 4.2 and Na2SO4/NaCl ratio: 3.1) while the NF membranes modified by γ-BL showed the greatest retention selectivity (MgCl2/NaCl ratio: 5.5 and Na2SO4/NaCl ratio: 4.2). All the zwitterionic membrane possessed high Na2SO4 and MgSO4 rejections (97–99%) and enhanced anti-fouling performance with 100% recovery capability. This work provided a facile and straightforward way to prepare zwitterionic membranes with significantly improved water permeation and retention selectivity of divalent/monovalent ions.

Short carboxyl terminal parathyroid hormone peptides modulate human parathyroid hormone signaling in mouse osteoblasts

BackgroundNovel human parathyroid hormone (hPTH) peptides of unknown biological activity have recently been identified in the serum of subjects with normal renal function, chronic renal failure, and end-stage renal disease through the application of liquid chromatography-high resolution mass spectrometry. Purposeof experiments: To determine the bioactivity of these peptides, we synthesized hPTH28-84, hPTH38-84, and hPTH45-84 peptides by solid phase peptide synthesis and tested their bioactivity in MC3T3-E1 mouse osteoblasts, either individually or together with the native hormone, hPTH1-84, by assessing the accumulation of 3´,5´-cyclic adenosine monophosphate (cAMP) and the induction of alkaline phosphatase activity. ResultsIncreasing doses of hPTH1-84 (1–100 nM) increased the accumulation of cAMP and alkaline phosphatase activity in osteoblasts. hPTH28-84, hPTH38-84, and hPTH45-84 in concentrations of 1–100 nM were biologically inert. Surprisingly, 100 nM hPTH38-84 and hPTH45-84 increased the accumulation of cAMP in osteoblasts treated with increasing amounts of hPTH1-84. Human PTH28-84 had no effects on cAMP activity alone or in combination with hPTH1-84. Conversely, 100 nM hPTH38-84, hPTH45-84, and hPTH28-84 blocked the activation of alkaline phosphatase activity by hPTH1-84. ConclusionsThe data show that the short carboxyl-terminal hPTH peptides, hPTH38-84 and hPTH45-84, increase the amount of cellular cAMP generated in cultured osteoblasts in response to treatment with full-length hPTH1-84 when compared to full-length hPTH1-84 alone. Human PTH28-84 had no effect on cAMP activity alone or in combination with hPTH1-84. Human PTH28-84, hPTH38-84 and hPTH45-84 reduced the effects of hPTH1-84 in osteoblasts with respect to the induction of alkaline phosphatase activity compared to hPTH1-84 alone. Short carboxyl peptides of human PTH are biologically inert but when administered together with full-length hPTH1-84 modulate the bioactivity of hPTH1-84 in osteoblasts.

Syntheses, Crystal Structures, and Properties of New Coordination Polymers Incorporating 3,3‐Dimethylcyclopropane‐1,2‐dicarboxylate and 4,4′‐Bipyridine Ligands

Three coordination polymers, [Zn(dcd)(bipy)0.5]n (1‐Zn), [Co(dcd)(bipy)0.5]n (2‐Co), and [Cu(bipy)2(H2O)1.5·(Hdcd)2·(H2O)3.5]4n (3‐Cu) (dcd = 3,3‐dimethylcyclopropane‐1,2‐dicarboxylate dianion, bipy = 4,4′‐bipyridine) were prepared by hydrothermal reactions. They were characterized by elemental analyses, FT‐IR spectra, single‐crystal X‐ray diffraction, X‐ray powder diffraction, photoluminescent and magnetic techniques. Single‐crystal X‐ray diffraction studies reveal that 1‐Zn and 2‐Co are isostructural and characteristic for 1D metal‐organic chains constructed by dcd bridging. Both of them contain mononuclear metal ions simultaneously bridged with short carboxylate bridges and long bipy spacers, resulting in a 2D grid framework. 3‐Cu is a neutral sandwiched ionic solid consisting of the positively charged trinuclear copper‐based coordination polymer and discrete Hdcd anions. 3‐Cu features two kinds of independent layers, which are further packed into a 3D supramolecular structure by strong hydrogen bonding interactions. Furthermore, 1‐Zn displays fluorescent emission assigned to the intra‐ligand fluorescence emission. Both 2‐Co and 3‐Cu exhibit antiferromagnetic coupling interactions. The carboxylate bridges existed in μ3‐dcd ligands can effectively mediate the antiferromagnetic interaction between CoII ions in 2‐Co, whereas strong hydrogen bonds are effective magnetic exchange pathways in 3‐Cu.

Salting-out and salting-in effects of organic compounds and applications of the salting-out effect of Pentasodium phytate in different extraction processes

The influence of different uncharged and charged organic compounds on the Lowest Solution Temperature (LST) of a water/dipropylene glycol propyl ether (DPnP) mixture is investigated. Depending on the nature of the additive, a salting-out or salting-in behavior could be observed. For the binary mixture, a salting-out effect is associated with a decrease of the LST with increasing additive concentrations. The reverse effects are observed with increasing salting-in additive concentrations. Typical sugars, short carboxylate sodium salts, ammonium organic salts and amino-acids were found to be salting-out, whereas all studied sweeteners and organic acids showed a salting-in behavior. The Pentasodium phytate ((Phy5−, 5Na+)) was found being the most efficient organic salting-out compound. Three possible applications were investigated in order to compare the salting-out effect of (Phy5−, 5Na+) to classical inorganic salts. First, the liquid-liquid extraction of 5-hydroxymethylfurfural (HMF) was investigated and compared to former results obtained using lithium, sodium and aluminium sulfate salts. Secondly, we considered a liquid-liquid, ethanol-water separation and compared the results to the one obtained using ammonium sulfate and potassium pyrophosphate. Finally, the salting-out effect of (Phy5−, 5Na+) on glycerol was investigated and also compared to the inorganic salts, sodium chloride and lithium sulfate as well as potassium and sodium phosphates.Due to higher water solubility, (Phy5−, 5Na+) allowed a more pronounced separation of HMF than the tested sulfate salts. This high water solubility drives also to a more pronounced separation of ethanol in comparison to ammonium sulfate; potassium pyrophosphate being the most water soluble and most efficient salt to separate ethanol and water. The use of (Phy5−, 5Na+) and potassium pyrophosphate showed a salting-out effect on glycerol in contrast to the inorganic salts sodium chloride and lithium sulfate for which a salting-in effect on glycerol was observed. The salting-out effect of sodium triphosphate was limited by its water solubility.

The recombinant equine LHβ subunit combines divergent intracellular traits of human LHβ and CGβ subunits

The pituitary LHβ and placental CGβ subunits are products of different genes in primates. The major structural difference between the two subunits is in the carboxy-terminal region, where the short carboxyl sequence of hLHβ is replaced by a longer O-glycosylated carboxy-terminal peptide in hCGβ. In association with this structural deviation, there are marked differences in the secretion kinetics and polarized routing of the two subunits. In equids, however, the CGβ and LHβ subunits are products of the same gene expressed in the placenta and pituitary (LHβ), and both contain a carboxy-terminal peptide. This unusual expression pattern intrigued us and led to our study of eLHβ subunit secretion by transfected Chinese hamster ovary and Madin–Darby canine kidney cells. In continuous labeling and pulse-chase experiments, the secretion of the eLHβ subunit from the transfected Chinese hamster ovary cells was inefficient (medium recovery of 16%–25%) and slow (t1/2 > 6.5 hours). This indicated that, the secretion of the eLHβ subunit resembles that of hLHβ rather than hCGβ. In Madin–Darby canine kidney cells grown on Transwell filters, the eLHβ subunit was preferentially secreted from the apical side, similar to the hCGβ subunit secretory route (∼65% of the total protein secreted). Taken together, these data suggested that secretion of the eLHβ subunit integrates features of both hLHβ and hCGβ subunits. We propose that the evolution of this intracellular behavior may fulfill the physiological demands for biosynthesis of the LH and CG β-subunits in the pituitary and placenta, respectively.

One-pot Functionalization of Short Carboxyl Multi-walled Carbon Nanotubes with Ninhydrin and Thiourea via Microwave and Thermal Methods and Their Effect on MKN-45 and MCF7 Cancer Cells

The one-pot chemical functionalization of short carboxyl multi-walled carbon nanotubes (Sh-MWCNT-COOH) with ninhydrin and thiourea for producing 3a,8a-dihydroxy-2-thioxo-1,3,3a,8a-tetrahydroindeno[1,2-d]imidazol-8(2H)-one (Sh-MWCNT-inden) via thermal and microwave methods have been investigated. The product was characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscope, elemental analysis, thermogravimetric analysis and cellular investigations. Sh-MWCNT-inden can be homogeneously dispersed in dimethyl formamide without sonication and the dispersed Sh-MWCNTs does not sediment in three months. MTT assay was used to examine the behavior of cell proliferation after 72 hours of cell culture experiments. Cellular investigations were performed for two kind cells, human breast and gastric cancer cells. Cellular results showed high toxicity of Sh-MWCNT-inden on the gastric cancer cells (77%) compared with breast cells (65%).

Modification of Fatty Acids in Membranes of Bacteria: Implication for an Adaptive Mechanism to the Toxicity of Carbon Nanotubes

We explored whether bacteria could respond adaptively to the presence of carbon nanotubes (CNTs) by investigating the influence of CNTs on the viability, composition of fatty acids, and cytoplasmic membrane fluidity of bacteria in aqueous medium for 24 h exposure. The CNTs included long single-walled carbon nanotubes (L-SWCNTs), short single-walled carbon nanotubes (S-SWCNTs), short carboxyl single-walled carbon nanotubes (S-SWCNT-COOH), and aligned multiwalled carbon nanotubes (A-MWCNTs). The bacteria included three common model bacteria, Staphyloccocus aureus (Gram-positive), Bacillus subtilis (Gram-positive), and Escherichia coli (Gram-negative), and one polybrominated diphenyl ether degrading strain, Ochrobactrum sp. (Gram-negative). Generally, L-SWCNTs were the most toxic to bacteria, whereas S-SWCNT-COOH showed the mildest bacterial toxicity. Ochrobactrum sp. was more susceptible to the toxic effect of CNTs than E. coli. Compared to the control in the absence of CNTs, the viability of Ochrobactrum sp. decreased from 71.6-81.4% to 41.8-70.2%, and E. coli from 93.7-104.0% to 67.7-91.0% when CNT concentration increased from 10 to 50 mg L(-1). The cytoplasmic membrane fluidity of bacteria increased with CNT concentration, and a significant negative correlation existed between the bacterial viabilities and membrane fluidity for E. coli and Ochrobactrum sp. (p < 0.05), indicating that the increase in membrane fluidity induced by CNTs was an important factor causing the inactivation of bacteria. In the presence of CNTs, E. coli and Ochrobactrum sp. showed elevation in the level of saturated fatty acids accompanied with reduction in unsaturated fatty acids, compensating for the fluidizing effect of CNTs. This demonstrated that bacteria could modify their composition of fatty acids to adapt to the toxicity of CNTs. In contrast, S. aureus and B. subtilis exposed to CNTs increased the proportion of branched-chain fatty acids and decreased the level of straight-chain fatty acids, which was also favorable to counteract the toxic effect of CNTs. This study suggests that the bacterial tolerances to CNTs are associated with both the adaptive modification of fatty acids in the membrane and the physicochemical properties of CNTs. This is the first report about the physiologically adaptive response of bacteria to CNTs, and may help to further understand the ecotoxicological effects of CNTs.

Three 3‐Amino‐1, 2, 4‐Triazole‐Based Magnetic Complexes Incorporated with Different Carboxylate‐Containing Coligands: Synthesis, Structures, and Magnetic Properties

AbstractThree 3‐amino‐1, 2, 4‐triazole (atz)‐based paramagnetic complexes, [Mn(atz)(pa)]n (1), {[Mn(atz)1.5(hip)]·H2O}n (2), and [Mn(H2O)2(atz)2(nb)2] (3) (H2pa = o‐phthalic acid, H2hip = 5‐hydroxylisophthalic acid, and Hnb = p‐nitrobenzoic acid) were prepared by introducing different carboxylate‐containing aromatic coligands, and structurally and magnetically characterized. Helical MnII‐atz and bent MnII‐pa2– chains are crosslinked by sharing the same metal sites to generate a honeycomb‐shaped framework of 1. The undulated MnII‐atz layers constructed from 22‐member metallomacrocycles are periodically supported by ditopic hip2– ligands to lead to a pillared‐layer structure of 2. In contrast, complex 3 is a centrosymmetric mononuclear entity, which is assembled into a three‐dimensional supramolecular network by abundant hydrogen‐bonding interactions. The structural difference of 1–3 is significantly due to the combinations of the flexible coordination modes adopted by the mixed atz and carboxylate groups. Weak and comparable antiferromagnetic couplings are observed in the nearest neighbors of 1–3, which are cooperatively transmitted either by short carboxylate and/or atz heterobridges or by weak non‐covalent interactions.

Cytotoxicity of carboxyl carbon nanotubes on human embryonic lung fibroblast cells and its mechanism

The wide use in various fields and the great potentials in biomedical applications of carbon nanotubes highlight the need to study their toxicity and biocompatibility for recent years. This work aimed to investigate the cytotoxicity of carbon nanotubes on human embryonic lung fibroblast cells and their inter-related affecting factors. Three carboxyl modified carbon nanotubes, short carboxyl single-walled carbon nanotubes (SWCNTs-COOH), short carboxyl double-walled carbon nanotubes (DWCNTs-COOH) and short carboxyl multi-walled carbon nanotubes (MWCNTs-COOH) were chosen as subjects for the evaluation of carbon nanotubes cytotoxity. Different concentrations of carboxyl carbon nanotubes were incubated with human embryonic lung fibroblast (HELF) cells for 48 h, respectively, and the electron microscopy was used to observe the cell growth and morphology. The results showed that MWCNTs-COOH, which had a better dispersion in water was much more cytotoxic than the other two carbon nanotubes. From Cell Counting Kit-8 assay and acridine orange staining, MWCNTs-COOH could inhibit the cell growth and induce cell apoptosis with a dose–effect relationship and oxidative stress may be one of the mechanisms.

The Distal End of Carboxyl-Terminus is Not Essential for the Assembly of Rat Eag1 Potassium Channels

The assembly of four pore-forming α-subunits into tetramers is a prerequisite for the formation of functional K+ channels. A short carboxyl assembly domain (CAD) in the distal end of the cytoplasmic carboxyl-terminus has been implicated in the assembly of Eag α-subunits, a subfamily of the ether-a-go-go K+ channel family. The precise role of CAD in the formation of Eag tetrameric channels, however, remains unclear. Moreover, it has not been determined whether other protein regions also contribute to the assembly of Eag subunits. We addressed these questions by studying the biophysical properties of a series of different rat Eag1 (rEag1) truncation mutants. Two truncation mutants without CAD (K848X & W823X) yielded functional phenotypes similar to those for wild-type (WT) rEag1 channels. Furthermore, non-functional rEag1 truncation mutants lacking the distal region of the carboxyl-terminus displayed substantial dominant-negative effects on the functional expression of WT as well as K848X and W823X channels. Our co-immunoprecipitation studies further revealed that truncation mutants containing no CAD indeed displayed significant association with rEag1-WT subunits. Finally, surface biotinylation and protein glycosylation analyses demonstrated that progressive truncations of the carboxyl-terminus resulted in aggravating disruptions of membrane trafficking and glycosylation of rEag1 proteins. Overall, our data suggest that the distal carboxyl-terminus, including CAD, is dispensable for the assembly of rEag1 K+ channels, but may instead be essential for ensuring proper protein biosynthesis. We propose that the S6 segment and the proximal carboxyl-terminus may constitute the principal subunit recognition site for the assembly of rEag1 channels.

Microwave plasma activation of a polyvinylidene fluoride surface for protein immobilization

Polyvinylidene fluoride (PVDF) was modified by CO2, N2 or N2/H2 plasmas, which permitted the attachment of short carboxyl or amino groups. A variation of the discharge parameters was performed, for their optimization, as well as for minimizing degradation in favour of acidic, amphiphilic or basic functionalization, respectively. The optimum parameters of discharge for CO2, N2 or N2/H2 plasmas were P = 50 W, gas flow rate Q = 16 × 10−8 m3 s−1, exposure time t = 30–60 s, d = 0.1 m, pressure 15 Pa. The new surfaces were characterized by wettability measurements, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) methods. In a second step, the proteins (triglycine (TG) and protein A) were adsorbed or chemically grafted onto the carboxyl or amino functionalized surface, after EDC/NHS (1-ethyl-3-(-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide) activation of proteins. ATR-FTIR, XPS and AFM investigations confirmed the presence of protein on the surface. The XPS C1s core levels at 286.3 eV (C–N), 288 eV (amide bond) and 298 eV (carboxylic acid), together with variation of the O1s and N1s signals, illustrated the immobilization of proteins. It was established that TG was better attached on surfaces activated with N2/H2 plasma, while protein A was more tightly anchored on CO2, N2 plasma-activated surfaces. The former procedure allowed higher surface densities, while the latter permitted a better chemical control. The results proved that plasma-treated PVDF is a good substrate for protein coating, which can be further used for microorganisms' detection, as evidenced by the immunoassay test.

Distal End of Carboxyl Terminus Is Not Essential for the Assembly of Rat Eag1 Potassium Channels

The assembly of four pore-forming α-subunits into tetramers is a prerequisite for the formation of functional K(+) channels. A short carboxyl assembly domain (CAD) in the distal end of the cytoplasmic carboxyl terminus has been implicated in the assembly of Eag α-subunits, a subfamily of the ether-à-go-go K(+) channel family. The precise role of CAD in the formation of Eag tetrameric channels, however, remains unclear. Moreover, it has not been determined whether other protein regions also contribute to the assembly of Eag subunits. We addressed these questions by studying the biophysical properties of a series of different rat Eag1 (rEag1) truncation mutants. Two truncation mutants without CAD (K848X and W823X) yielded functional phenotypes similar to those for wild-type (WT) rEag1 channels. Furthermore, nonfunctional rEag1 truncation mutants lacking the distal region of the carboxyl terminus displayed substantial dominant-negative effects on the functional expression of WT as well as K848X and W823X channels. Our co-immunoprecipitation studies further revealed that truncation mutants containing no CAD indeed displayed significant association with rEag1-WT subunits. Finally, surface biotinylation and protein glycosylation analyses demonstrated that progressive truncations of the carboxyl terminus resulted in aggravating disruptions of membrane trafficking and glycosylation of rEag1 proteins. Overall, our data suggest that the distal carboxyl terminus, including CAD, is dispensable for the assembly of rEag1 K(+) channels but may instead be essential for ensuring proper protein biosynthesis. We propose that the S6 segment and the proximal carboxyl terminus may constitute the principal subunit recognition site for the assembly of rEag1 channels.

Molecular cloning and characterization of a hamster Cav1.3 Ca2+ channel variant with a long carboxyl terminus

We have cloned a hamster Cav1.3 variant with a long carboxyl terminus. This differs from the first hamster Cav1.3 clone which has a short carboxyl terminus. When relative expression levels of the two variants were examined using quantitative RT-PCR, the long Cav1.3 transcripts were detected abundantly in the brain and testis, moderately in the heart, pancreas, and kidney, and weakly in the lung. Comparatively, the short Cav1.3 transcripts were detected less abundantly in most of the tissues. The two Cav1.3 variants were reconstituted in Xenopus oocytes and their electrophysiological properties were characterized using a two-electrode voltage clamping method. The long Cav1.3 variant was ~5-fold better expressed than the short Cav1.3 variant. When Ca2+ was used as a charge carrier, the long Cav1.3 variant containing an IQ (Ile-Gln) motif displayed strong calcium-dependent inactivation, while the short variant that was deficient of an IQ motif showed little calcium-dependent inactivation. Examination of other biophysical properties revealed that potentials for activation threshold, peak current, and half-activation and inactivation of the long Cav1.3 were significantly lower than those of the short Cav1.3. These findings suggest that the long carboxyl tail plays crucial roles in not only facilitating calcium-dependent inactivation, but also improving expression and negative shifting of the activation and inactivation properties.

Recent advancements in the biosynthetic mechanisms for polyketide-derived mycotoxins.

Polyketides (PKs) are a large group of natural products produced by microorganisms and plants. They are biopolymers of acetate and other short carboxylates and are biosynthesized by multifunctional enzymes called polyketide synthases (PKSs). This review discusses the biosynthesis of four toxic PK, aflatoxins, fumonisins, ochratoxins (OTs), and zearalenone. These metabolites are structurally diverse and differ in their mechanisms of toxicity. However, they are all of concern in food safety and agriculture because of their toxic properties and their frequent accumulation in crops used for food and feed. The focus is on the recent advancements in the understanding of the molecular mechanisms for the biosynthesis of these mycotoxins. Several of the mycotoxin PKSs have been genetically and biochemically studied while other PKSs remain to be investigated. Multiple post-PKS modifications are often required for the maturation of the mycotoxins. Many of these modification steps for aflatoxins and fumonisins are well established while the post-PKS modifications for zearalenone and OTs remain to be biochemically characterized. More efforts are needed to completely illustrate the biosynthetic mechanisms for this important group of PKs.

The SEPALLATA-Like Gene OsMADS34 Is Required for Rice Inflorescence and Spikelet Development

Grass plants develop distinct inflorescences and spikelets that determine grain yields. However, the mechanisms underlying the specification of inflorescences and spikelets in grasses remain largely unknown. Here, we report the biological role of one SEPALLATA (SEP)-like gene, OsMADS34, in controlling the development of inflorescences and spikelets in rice (Oryza sativa). OsMADS34 encodes a MADS box protein containing a short carboxyl terminus without transcriptional activation activity in yeast cells. We demonstrate the ubiquitous expression of OsMADS34 in roots, leaves, and primordia of inflorescence and spikelet organs. Compared with the wild type, osmads34 mutants developed altered inflorescence morphology, with an increased number of primary branches and a decreased number of secondary branches. In addition, osmads34 mutants displayed a decreased spikelet number and altered spikelet morphology, with lemma/leaf-like elongated sterile lemmas. Moreover, analysis of the double mutant osmads34 osmads1 suggests that OsMADS34 specifies the identities of floral organs, including the lemma/palea, lodicules, stamens, and carpel, in combination with another rice SEP-like gene, OsMADS1. Collectively, our study suggests that the origin and diversification of OsMADS34 and OsMADS1 contribute to the origin of distinct grass inflorescences and spikelets.

Growth of Pseudomonas sp. TX1 on a wide range of octylphenol polyethoxylate concentrations and the formation of dicarboxylated metabolites

Pseudomonas sp. TX1, is able to use octylphenol polyethoxylates (OPEO(n), or Triton X-100; average n = 9.5) as a sole carbon source. It can grow on 0.05-20% of OPEO(n) with a specific growth rate of 0.34-0.44 h(-1). High-performance liquid chromatography-mass spectrometer analysis of OPEO(n) degraded metabolites revealed that strain TX1 was able to shorten the ethoxylate chain and produce octylphenol (OP). Furthermore, formation of the short carboxylate metabolites, such as carboxyoctylphenol polyethoxylates (COPEO(n), n = 2, 3) and carboxyoctylphenol polyethoxycarboxylates (COPEC(n), n = 2, 3) began at the log stage, while octylphenol polyethoxycarboxylates (OPEC(n), n = 1-3) was formed at the stationary phase. All the short-ethoxylated metabolites, OPEO(n), OPEC(n), COPEO(n), and COPEC(n), accumulated when the cells were in the stationary phase. This study is the first to demonstrate the formation of COPEO(n) and COPEC(n) from OPEO(n) by an aerobic bacterium.

CaV2.1 P/Q-type calcium channel alternative splicing affects the functional impact of familial hemiplegic migraine mutations: Implications for calcium channelopathies

Alternative splicing is known to generate multiple functionally distinct calcium channel variants that exhibit distinct spatial and temporal expression patterns. In humans, naturally occurring mutations in genes encoding calcium channel pore forming α1-subunits are associated with several severe hereditary disorders although it remains to be described whether there exists any relationship between the physiological effects of these mutations and calcium channel splice variation. In the present study, we systematically compare the biophysical effects of three type-1 familial hemiplegic migraine (FHM-1) mutations in two predominant splice variants of the neuronal CaV2.1 P/Q-type channel. All three FHM-1 mutations cause a greater hyperpolarizing shift in voltage-dependent properties when expressed in the short carboxyl terminus variant (CaV2.1 Δ47) compared to the long variant (CaV2.1 +47). Furthermore, the FHM-1 mutations also exhibit differential splice variant-specific effects on recovery from inactivation and accumulation of inactivation during tonic and burst firing. Our findings provide important insight concerning the role of calcium channel alternatively spliced variants and the molecular pathophysiology of FHM-1 and potentially of other calcium channelopathies.

2-Hydroxybicyclo[2.2.1]heptane-2-endo-carboxylic acid

In the title compound, C8H12O3, the methyl­ene function of glycolic acid is incorporated in the sterically demanding lipophilic norbornane backbone. Pairs of longer inter­molecular hydroxyl OH⋯carboxyl O hydrogen bonds lead to the formation of centrosymmetric dimers. The dimers are connected to form sheets parallel to the bc plane by shorter carboxyl OH⋯hydroxyl O bonds. Hydro­phobic contacts connect the hydrogen-bonded sheets.

Para‐Dialkylaminophenyl Dyes for Efficient Nanocrystalline TiO2 Sensitization in Far‐red Region

AbstractFour para‐dialkylaminophenyl (PDAAP1–PDAAP4) bearing carboxyl groups were studied for application to the dye‐sensitized solar cells (DSC). It was found the short spacer CH2 between carboxyl and dialkylaminophenyl chromophore in PDAAP3 and PDAAP4 led to highly efficient monochromatic incident photon‐to‐current conversion efficiencies (IPCE), however the long alkyl group C4H9 attached on aniline moieties in PDAAP2 and PDAAP4 favored improvement of open‐circuit photovoltage. Thus, the solar cell sensitized by PDAAP4, having both short carboxyl groups CH2COOH and long alkyl groups C4H9, exhibited the IPCE maximum of 73% at 670 nm and overall energy conversion efficiency η of 3.06%, representing the highest IPCE and η values so far in dialkylaminophenyl‐based organic dye‐sensitized semiconductor solar cells. Taking advantage of the highly efficient sensitizing ability of PDAAP4 in far‐red region, the data of IPCE above 630 nm of the solar cells were improved greatly by cosensitization with both N3 and PDAAP4. The influences of the TiO2 film thickness and the concentration of 4‐tert‐butylpyridine (TBP) in electrolyte were also investigated.