13C NMR spectra of some naturally occurring binaphthoquinones and related compounds

¹³C NMR chemical shift assignments have been shown to be diagnostic for the establishment of the dimeric linkage of some naturally occurring binaphthoquinones. The unsymmetric ¹³C and ¹H spin-spin coupled pattern observed in the ¹H coupled ¹³C NMR spectrum of plumbagin for C-6 has also been noticed earlier with the related compound juglone. The nature of these effects has been substantiated for the first time using benzene induced solvent shifts and D₂O exchange. ¹³C chemical shift assignments of plumbagin reported earlier for C-6 and C-8 have been revised.     

Structure of histamine releasing guaianolides from Thapsia species

The structures of six hexaoxygenated guaianolides esterified with four non isomeric carboxylic acids have been established by ¹H NMR and ¹³C NMR spectroscopy. The acyl residues have been located by chemical ionisation mass spectrometry. Some of the acyl residues are novel for sesquiterpene lactones. The acyl residues in two additional guaianolides esterified with isomeric acids have been located by partial hydrolysis.     

H-NMR of G-U-C and G-U-C-C in D2O: assignment of nonexchangeable protons and analysis of solution conformation

The ribonucleotide oligomers G-U-C and G-U-C-C have been synthesized enzymatically. These oligomers are cognates of the m⁷G⁴⁶-U⁴⁷-C⁴⁸-m⁵C⁴⁹ sequence found in the variable loop of t-RNA^phe. The ¹H-NMR chemical shifts of the base and ribose Hl; protons as well as the couplings. J_1'–2' of the ribose protons have been examined as a function of temperature. Assignments for these resonances have been completed, and used in the analysis of solution conformation for these oligomers. The results are consistent with the basic features of the A-RNA structure and suggest the absence of alternative ordered solution structures.     

1H-NMR Of U-G-A and U-G-A-A in D2O:: Assignment of nonexchangeable protons and analysis of solution conformation

The ribonucleotide oligomers U-G-A and U-G-A-A have been synthesized enzymatically. These oligomers are cognates of the U³³-Gm³⁴-A³⁵-A³⁶ sequence found in the anticodon loop of t-RNA^phe. The ¹H-NMR chemical shifts of the base and ribose HI' protons as well as the couplings. J_1'–2', of the ribose protons have been examined as a function of temperature. Assignments for these resonances have been completed, and used in the analysis of solution conformation for these oligomers. The results are consistent with the A-RNA structure and suggest the absence of alternative ordered solution structures.     

Intermediate in SV40 DNA Chain Growth

PREVIOUS studies of the DNA replication of simian virus 40 (SV40), an oncogenic member of the papoyavirus group, have been concerned with separation and characterization of replicative intermediates^1–4. Circular replicating intermediates have been identified for SV40^1–3, as well as for the similar replication system of polyoma viral DNA5,6. The replicative intermediates of SV40 DNA have been observed by electron microscopy to contain two forks, three branches and no free ends^1–3 as is the case for the circular replicating molecules of polyoma, bacteriophage λ⁷, Escherichia coli⁸ and colicin E1 in mini-cells^9,10. An important property of replicative intermediates of SV40 DNA that has also been observed in replicating molecules of colicin E1¹⁰ is that most molecules contain a superhelical region in the unreplicated portion of the molecule¹.     

Ca-sensitive K channels in phagocytic cell membranes

In phagocytic cells evidence for properties of Ca²⁺-sensitive K⁺-selective channels comes mostly from electrophysiological studies. Macrophages and macrophage-like cells are compared with fibroblasts (L-cells) where the Ca⁺-dependent K⁺ conductance is better understood. This model shares a mesenchymal origin and an accessory phagocytic capacity with the professional phagocytes. In macrophages several values of transmembrane potentials have been measured by different groups, using various techniques. Microelectrode measurements have demonstrated a voltage-dependent K⁺ conductance involved in transition from low to high membrane potentials. Current-voltage relationships in mouse peritoneal exudate cells have revealed a region of negative slope resistance. Slow calcium spikes were found in a subpopulation of cells from human dialysis fluid that appear to be distinct from typical macrophages. Action potentials have been recorded from human monocyte-derived macrophages. Their ionic mechanism has not yet been established. Spontaneous and electrically elicited slow membrane hyperpolarizations have been described in macrophages and macrophage-like cells. Similar activity is well known in L-cells and in both cases it is possible to identify a Ca²⁺-sensitive K⁺ conductance as the underlying mechanism. Phagocytosis is a cell function that has been related to membrane hyperpolarization and to slow hyperpolarizing activity. In some cases no changes of electrical activity have been observed during the phagocytic process. Chemotactic factors induce membrane hyperpolarizations in macrophages, but the relation between electrical change and cell motility has not been established. Exocytosis, a is another Ca²⁺ sensitive cell function that awaits correlation with electrochemical changes. The evidences accumulated to date are compatible with several models for gating and modulation of the voltage-independent K⁺ conductance by Ca²⁺. The use of higher resolution techniques, such as patch-clamp, with well defined subpopulations of phagocytic cells may produce the missing link in the transduction of membrane signals into the specifically targeted cell functions.     

Synthesis and biological activity of five d-Cys analogs of human insulin

Five analogs of human insulin with d-Cys in different positions (A⁶, A⁷, A¹¹, A⁶⁺¹¹, B⁷) have been synthesized by the fragment condensation approach, combined with selective disulfide formation. All of them have physicochemical properties noticeably different from those of human insulin. They possess very low biological activity (0.03?1.2%, glucose oxidation in rat fat cells). In contrast, the potency for antibody binding ranges from 7 to 70% of that of insulin. The two analogs with d-Cys in positions A⁶ and A⁷ have been obtained in crystalline form.     

Hydrogen-deuterium exchange of the tryptophan residues in bovine α-lactalbumin

Effects of deuteration on the Raman spectrum of a tryptophan residue have been examined. The 1386 cm^?1 line of deuterated tryptophan residue has been found to be useful for tracing the hydrogen-deuterium exchange reaction of this residue in a protein. An examination on bovine α-lactalbumin at pH 6.4 and at 20°C indicates that two of the four tryptophan residues exchange with a rate constant much greater than 9 × 10^?4 sec^?1, while the other two exchange with a rate constant of 4 × 10^?5 sec^?1. The latter two have been assigned to Trp 28 and Trp 108 of this protein. The kinetics of hydrogen-deuterium exchange reaction of completely “free” tryptophan residue have been examined by a proton magnetic resonance study on tryptophan itself. By taking the result of this examination into account, the chance of exposure to the solvent for Trp 28 or Trp 108 has been estimated to be 3 × 10^?6 at pH 6.4 and at 20°C.     

Synthesis and biological activity of five -Cys analogs of human insulin

Five analogs of human insulin with -Cys in different positions (A⁶, A⁷, A¹¹, A⁶⁺¹¹, B⁷) have been synthesized by the fragment condensation approach, combined with selective disulfide formation. All of them have physicochemical properties noticeably different from those of human insulin. They possess very low biological activity (0.03−1.2%, glucose oxidation in rat fat cells). In contrast, the potency for antibody binding ranges from 7 to 70% of that of insulin. The two analogs with -Cys in positions A⁶ and A⁷ have been obtained in crystalline form.     

Synthesis,spectroscopic, and antibacterial activity of tetraazamacrocyclic complexes of trivalent chromium,manganese, and iron

A new series of macrocyclic complexes of type [M(TML)X]X₂, where M = Cr(III), Mn(III), or Fe(III), TML is tetradentate macrocyclic ligand, and X = Cl^?, NO₃^?, CH₃COO^? for Cr(III), Fe(III) and X = CH₃COO^? for Mn (III), has been synthesized by condensation of benzil and succinyldihydrazide in the presence of metal salt. The complexes have been so formulated due to the 1:2 electrolytic nature of these complexes as shown by conductivity measurements. The complexes have been characterized with the help of various physicochemical techniques such as elemental analysis, molar conductance, electronic and infrared spectral studies, and magnetic susceptibility. On the basis of these studies, a five-coordinate distorted square pyramidal geometry, in which two nitrogens and two carbonyl oxygen atoms are suitably placed for coordination toward the metal ion, has been proposed for all the complexes. The complexes have been tested for their in vitro antibacterial activity. Some of the complexes show remarkable antibacterial activities against some selected bacterial strains. The minimum inhibitory concentrations shown by these complexes have been compared with those shown by some standard antibiotics such as linezolid and cefaclor.     

Study of SOD Mimic and Nucleic Acid Interaction Activity Exerted by Enrofloxacin‐Based Copper(II) Complexes

Five new copper(II) complexes of type [Cu(erx)( L )Cl] (erx, enrofloxacin; thiophene‐2‐carbaldehyde ( L ¹ ); pyridine‐2‐carbaldehyde ( L ² ); 2,2′‐dipyridylamine ( L ³ ); 4,5‐diazafluoren‐9‐one ( L ⁴ ); bis(3,5‐dimethyl‐1‐pyrazolyl)methane ( L ⁵ )) have been synthesized and characterized by elemental analysis, reflectance, IR, and FAB‐MS. Complexes have been investigated for their interaction with calf thymus (CT) DNA utilizing the absorption‐titration method, viscometric and DNA thermal denaturation studies. The cleavage reaction on pUC19 DNA has been monitored by agarose gel electrophoresis. The results indicated that the Cu^II complexes can more effectively promote the cleavage of plasmid DNA at physiological pH and superoxide dismutase. The (SOD) activity of the complexes has been evaluated by the nitroblue tetrazolium assay, and the complexes catalyzed the dismutation of superoxide at pH 7.8 with IC₅₀ values of 0.35–1.25 μM . The complexes have also been screened for their antibacterial activity against five pathogenic bacteria.     

DFT investigation of the thermodynamics and mechanism of electrophilic chlorination and iodination of arenes

Quantum chemical calculations at the B3LYP/6-311G* level have been carried out in order to investigate the reaction mechanisms of the iodination of benzene and its monosubstituted derivatives with ICl, I⁺, I₃⁺ and reagents containing N–I and O–I bonds as the iodinating agents. The results are compared with those obtained for chlorination by Cl⁺ and Cl₂, both in the gas phase and in methanol solution using the PCM solvent model. We have also used the MP2/DGDZVP level of theory and the IEFPCM model to perform comparisons in a few cases. The thermodynamic parameters for the reactions have been calculated, the structures of the intermediate products (π- and σ-complexes) and transition states have been optimized, and the profiles of the free energy surfaces have been constructed.     

Synthesis and biological activity of (D)Ala2, Leu5-enkephalins containing hydrophilic or hydrophobic moieties

The synthesis in solution of some modified (D)Ala²,Leu⁵-enkephalins has been carried out. The lipophilic properties of the parent compound have been modified by amidation of the carboxyl function with alkylamines of increasing hydrophilicity to increase permeability of the blood-brain barrier. Attempts to reduce enzymatic degradation have been carried out either by reductive glucosamination or by amidation of the carboxyl function with 2-amino-2-deoxy-β-D-glucopyranose. Esterification of the carboxyl function of (D)Ala²,Leu⁵-enkephalin with polyethylenglycole 1000 has also been carried out. The effects induced by these modifications have been evaluated by in vitro and in vivo tests.     

Hydrogen Consumption by Methanogens on the Early Earth

It is possible that the first autotroph used chemical energy rather than light. This could have been the main source of primary production after the initial inventory of abiotic organic material had been depleted. The electron acceptor most readily available for use by this first chemoautotroph would have been CO₂. The most abundant electron donor may have been H₂ that would have been outgassing from volcanoes at a rate estimated to be as large as 10¹² moles yr^–1, as well as from photo-oxidation of Fe⁺². We report here that certain methanogens will consume H₂ down to partial pressures as low as 4 Pa (4 × 10^–5 atm) with CO₂ as the sole carbon source at a rate of 0.7 ng H₂ min^–1 g^–1 cell protein. The lower limit of pH₂ for growth of methanogens can be understood on the basis that the pH₂ needs to be high enough for one ATP to be synthesized per CO₂ reduced. The pH₂ values needed for growth measured here are consistent with those measured by Stevens and McKinley for growth of methanogens in deep basalt aquifers. H₂-consuming autotrophs are likely to have had a profound effect on the chemistry of the early atmosphere and to have been a dominant sink for H₂ on the early Earth after life began rather than escape from the Earth's atmosphere to space.     

Sequence of Formation of Phosphoglycolate and Glycolate in Photosynthesizing Chlorella pyrenoidosa

In Chlorella pyrenoidosa which have been photosynthesizing in either 1.5% ¹⁴CO₂ or 0.05% ¹⁴CO₂ in air, gassing with 100% O₂ results in rapid formation of phosphoglycolate which is apparently converted to glycolate. However, only about one-third to one-half of the rate of glycolate formation can be accounted for by this route. The remaining glycolate formation may be the result of the oxidation of sugar monophosphates. The rates of formation of both glycolate and phosphoglycolate are about four times greater with algae that have been photosynthesizing in 1.5% ¹⁴CO₂ than with algae which have been photosynthesizing with air, when the algae are then gassed with 100% O₂.     

Purification and properties of fluoroacetate dehalogenase from <Emphasis Type="Italic">Pseudomonas fluorescens</Emphasis> DSM 8341

The degradation of fluoroacetate by microorganisms has been established for some time, although only a handful of dehalogenases capable of hydrolyzing the stable C–F bond have been studied. Pseudomonas fluorescens DSM 8341 was originally isolated from soil and readily degrades fluoroacetate, thus it was thought that its dehalogenase might have some desirable properties. The enzyme was purified from cell-free extracts and characterised: it is a monomer of 32,500 Da, with a pH optimum of 8 and is stable between pH 4 and 10; its activity is stimulated by some metal ions (Mg²⁺, Mn²⁺ and Fe³⁺), but inhibited by others (Hg²⁺, Ag²⁺). The enzyme is specific for fluoroacetate, and the K _m for this substrate (0.68 mM) is the lowest determined for enzymes of this type that have been investigated to date.     

In vitro iodination of plant ribonucleic acids

The optimum conditions for in vitro iodination of RNAs have been established which yield specific radioactivities ranging from 10 × 10⁴ to 10 × 10⁶ cpm/μg. A nomogram has been constructed by correlating specific radioactivities of RNA with concentration of KI, RNA, and ¹²⁵I. This nomogram can be used to determine the conditions for the desired specific radioactivities for any unknown RNA. The in vitro iodinated RNA has been compared with in vivo labeled RNA for hybridization characteristics. Competition hybridization between ¹²⁵I-labeled chloroplast-rRNA and unlabeled pea (Pisum sativum) chloroplast-rRNA was identical to that found using [³²P]chloroplast-rRNA. Thermal stability of DNA-¹²⁵I-rRNA hybrids was similar to the thermal stability of DNA-[³²P]rRNA hybrids. The iodinated RNA was not found to have undergone any changes in its hydrogen-bonding properties.     

Metal-based new sulfonamides: Design,synthesis, antibacterial,antifungal, and cytotoxic properties

Cobalt(II), copper(II), nickel(II) and zinc(II) metal complexes with 5-chlorosalicyladehyde derived Schiff base sulfonamides have been synthesized and characterized. Structure and bonding nature of all the synthesized compounds have been deduced from physical, analytical, and spectral (IR, ¹H NMR, ¹³C NMR, Mass, electronic) data. An octahedral geometry has been proposed for all the metal complexes. The ligands and their metal complexes have been screened for their in vitro antibacterial, antifungal, and cytotoxic properties and results are reported.     

Nd3+‐Yb3+/Nd3+‐Yb3+‐Li+ co‐doped Gd2O3 phosphors for up and down conversion luminescence

Frequency up‐conversion (UC) emission from the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped gadolinium oxide (Gd₂O₃) phosphors prepared by the solution combustion technique in the visible range have been studied by using 980 nm near infrared (NIR) laser diode excitation. The crystalline structure and formation of the cubic phase has been confirmed with the help of X‐ray diffraction (XRD) studies. XRD peak shifts have been found towards the lower diffraction angle side in the case of the Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors. Surface morphology and particle size information have been observed by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) analysis. Down‐conversion emission study under 351 nm excitation in the visible region for the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors has been performed. The UC emission bands lying in the green and red region arising from the Nd³⁺ ions have been enhanced by ~260 times, ~113 times due to incorporation of Li⁺ ions in the Nd³⁺‐Yb³⁺ co‐doped phosphors. Photometric characterization has been done for the Nd³⁺‐Yb³⁺/Nd³⁺‐Yb³⁺‐Li⁺ co‐doped phosphors. The present study suggests the capability of the synthesized phosphors in near‐infrared (NIR) to visible upconverter and luminescent device applications.     

Quantitative variations in the expression of the mouse serum antigen Ss and its sex-limited allotype Slp

A radial immunodiffusion assay for quantitation of the Ss and Slp serum antigens is described. Significant differences between the mean serum concentrations of Ss and Slp were found among various inbred strains. Some of these differences have been shown to be associated with the H-2 haplotype. The quantitative difference between Slp levels associated with the H-2 ^a and H-2 ^S haplotypes has been used as a marker for the S region in the analysis of certain H-2 recombinant strains [A.TH, B10.S(7R), B10.S(9R), and B10.BSVS]. Male mice of two strains with the H-2 ^b haplotype have been shown to have significantly lower levels of Ss compared to males of the other strains tested. Male mice of every strain examined were found to have significantly higher levels of Ss in their serum than females of the same strain. The molecular relationship and developmental patterns of the Ss and Slp antigens have also been investigated using the radial immunodiffusion assay.