NOESY NMR Research Articles

Study of the interaction between indole-based compounds and biologically relevant G-quadruplexes

G-quadruplexes (G4s) are high-order secondary structures that modulate several key cell processes such as telomere function, gene expression and DNA replication. In the past years G4s have emerged as promising targets for drug development due to the discovery of small molecules which bind and stabilize these structures. In this work, we report the synthesis of indole-based compounds and the study of their interaction with the biological relevant G4s c-MYC and human telomeric repeat 22AG using several biophysical techniques. The ligands are G4 specific and they can discriminate different G4 structures namely parallel and hybrid-1 topologies. The NMR study of interaction between the most promising indole-derivative (compound 3) and c-MYC quadruplex suggests that the ligand binds on the external tetrads with additional actions in the loops/grooves in a 2:1 ratio. The molecular docking calculations of compound 3 to c-MYC quadruplex corroborates with the 1H and NOESY NMR studies.Overall, the results suggest that indole-based ligands are promising candidates for future lead optimizations in drug development.

Mining 2:2 Complexes from 1:1 Stoichiometry: Formation of Cucurbit[8]uril-Diarylviologen Quaternary Complexes Favored by Electron-Donating Substituents.

A 1:1 binding stoichiometry of a host-guest complex need not consist of a single host and guest. Diarylviologens containing electron-donating substituents complexed with cucurbit[8]uril (CB[8]) in a 1:1 stoichiometry exhibit abnormally large binding enthalpies compared to typical enthalpy changes observed for 1:1 binary complexes. Here, several CB[8]-mediated host-guest complexes, which were previously reported as 1:1 binary complexes, are verified to be 2:2 quaternary complexes by a combination of isothermal titration calorimetry, 1H, NOESY, and ROESY NMR, and ion mobility mass spectrometry, clearly indicating a binding motif of two partially overlapping diarylviologens held in place with two CB[8] molecules. Formation of 2:2 quaternary complexes is favored by electron-donating substituents, while electron-withdrawing substituents typically result in 1:1 binary complexes. The stacking of two highly conjugated diarylviologens in one quaternary motif affords the complexes enhanced conductance when considered as a single-molecular conductor. Moreover, an additional conducting signal previously observed for this "supramolecular" conductor can be readily understood with our 2:2 complexation model, corresponding to a parallel conductance pathway. Therefore, a 2:2 quaternary complex model grants a greater understanding of such supramolecular complexes, enabling the design of engineered, hierarchical structures and functional materials.

Acinetodin and Klebsidin, RNA Polymerase Targeting Lasso Peptides Produced by Human Isolates of Acinetobacter gyllenbergii and Klebsiella pneumoniae

We report the bioinformatic prediction and structural validation of two lasso peptides, acinetodin and klebsidin, encoded by the genomes of several human-associated strains of Acinetobacter and Klebsiella. Computation of the three-dimensional structures of these peptides using NMR NOESY constraints verifies that they contain a lasso motif. Despite the lack of sequence similarity to each other or to microcin J25, a prototypical lasso peptide and transcription inhibitor from Escherichia coli, acinetodin and klebsidin also inhibit transcript elongation by the E. coli RNA polymerase by binding to a common site. Yet, unlike microcin J25, acinetodin and klebsidin are unable to permeate wild type E. coli cells and inhibit their growth. We show that the E. coli cells become sensitive to klebsidin when expressing the outer membrane receptor FhuA homologue from Klebsiella pneumoniae. It thus appears that specificity to a common target, the RNA polymerase secondary channel, can be attained by a surprisingly diverse set of primary sequences folded into a common threaded-lasso fold. In contrast, transport into cells containing sensitive targets appears to be much more specific and must be the major determinant of the narrow range of bioactivity of known lasso peptides.

Solubility and bioavailability enhancement of ciprofloxacin by induced oval-shaped mono-6-deoxy-6-aminoethylamino-β-cyclodextrin

Ciprofloxacin is a broad-spectrum fluoroquinolone antibiotic used to treat bacterial infections; however, its limited aqueous solubility inhibits its broader clinical uses. This study investigated the complexation effect of mono-6-deoxy-6-aminoethylamino-β-cyclodextrin on the aqueous solubility and bioavailability of ciprofloxacin. During complexation, the oval-shaped cavity induced by mono-aminoethylamine substitution on the primary rim of β-cyclodextrin, was considered to be a key factor according to NMR spectroscopy and molecular modeling studies. The ciprofloxacin with mono-6-deoxy-6-aminoethylamino-β-cyclodextrin complex was characterized using FE-SEM, DSC, FT-IR, T1 relaxation, 2D NOESY, and DOSY NMR spectroscopy and molecular modeling studies. The solubility property of ciprofloxacin complexed with mono-6-deoxy-6-aminoethylamino-β-cyclodextrin was enhanced by seven-fold compared to that of pure ciprofloxacin. Furthermore antibacterial activity of that complex against methicillin-resistant Staphylococcus aureus was enhanced and it clearly showed the growth inhibition. The mono-6-deoxy-6-aminoethylamino-β-cyclodextrin has the potential to be utilized for other oblong guest molecules besides ciprofloxacin based on the novel induced elliptical cavity.

New Pesticidal Diterpenoids from Vellozia gigantea (Velloziaceae), an Endemic Neotropical Plant Living in the Endangered Brazilian Biome Rupestrian Grasslands.

Vellozia gigantea is a rare, ancient, and endemic neotropical plant present in the Brazilian Rupestrian grasslands. The dichloromethane extract of V. gigantea adventitious roots was phytotoxic against Lactuca sativa, Agrostis stolonifera, and Lemna paucicostata, and showed larvicidal activity against Aedes aegypti. Phytotoxicity bioassay-directed fractionation of the extract revealed one new isopimaradiene, 8(9),15-isopimaradien-1,3,7,11-tetraone, and three new cleistanthane diterpenoids, 7-oxo-8,11,13-cleistanthatrien-3-ol, 3,20-epoxy-7-oxo-8,11,13-cleistanthatrien-3-ol, and 20-nor-3,7-dioxo-1,8,11,13-cleistanthatetraen-10-ol. These new structures are proposed based on interpretation of 1H, 13C, COSY, NOESY, HSQC, and HMBC NMR data. 8(9),15-isopimaradien-1,3,7,11-tetraone was especially phytotoxic with an IC50 value (30 μM) comparable to those of commercial herbicides clomazone, EPTC, and naptalam. In addition, 7-oxo-8,11,13-cleistanthatrien-3-ol provided 100% mortality at a concentration of 125 ppm against one-day-old Ae. aegypti larvae. Our results show that ancient and unique plants, like the endangered narrowly endemic neotropical species V. gigantea present in the Rupestrian grasslands, should also be protected because they can be sources of new bioactive compounds.

Thermoresponsive Pyrrolidone Block Copolymer Organogels from 3D Micellar Networks.

A new series of amphiphilic pyrrolidone diblock copolymers poly[N-(2-methacrylaoyxyethyl)pyrrolidone]-block-poly(methyl methacrylate) (PNMPm-b-PMMAn; where m is fixed at 37 and n is varied from 45 to 378) is developed. Spontaneously situ-gelling behaviors are observed in isopropanol when n varies from 117 to 230, whereas only dissolution or precipitation appears when n is beyond this region. Further analysis reveals that uniform thermoinduced reversible gel–sol transitions are observed in those organogels, which is attributed to the disassembly from micellar networks to micelles as confirmed by electron microscopy and other techniques. The gel–sol transition temperature is highly dependent on n and increases as n increases. Conformational interactions analyzed using 1H NMR and 2D Noesy NMR suggest that the thermoinduced stretch of solvophilic PNMP segments within micelles and the sequencing variation in the isopropanol molecules are the major cause of the gel–sol transitions.

Metabolic Profiling of Human In-patient Stools: The Influence of C. difficile Infection and Recurrence

BackgroundInitial C. difficile infection (CDI) and recurrence is dependent on host susceptibility. Hospital patients have a diverse range of other comorbidities and concomitant medications that cannot be duplicated in animal models. We hypothesize that the intersection of the luminal biome and host is represented by the metabolites. Their contribution facilitates CDI clearance or recurrence.MethodsDiscarded stool samples from 4 groups of in-patients (UC IRB 2014–8646) were used. Case controls (CC,n = 20) have diarrhea but are CDI-. Initial CDI+ (I, n = 20) clear infection. Initial CDI+ who become recurrent (IR, n = 18) have samples from initial infection. Known CDI+ Recurrent (KR, n = 10) have samples from second to fourth CDI. Stools were kept at 4°C until aliquoted, weighed and frozen at -80°C. We lyophilized each aliquot and performed metabolome analysis on 50 mg of dry sample. The NMR-Based Metabolomics Core used 1D NOESY and 1D CPMG NMR experiments to generate raw metabolic concentrations. Metabolite IDs were validated with 2D 1H-1H TOCSY and 2D 1H-13C HSQC experiments.Results46 metabolites could be definitively identified and compared. Analysis of raw metabolite mM concentrations in CDI+ stools demonstrated more acetate (median ± median absolute deviation) (CC: 1.63 ± 1.54, I: 5.20 ± 3.21, IR: 4.21 ± 1.46, KR: 2.4 ± 2.15) and butyrate (CC: .1195 ± 0.1185, I: 0.4992 ± 0.3721, IR: 0.4196 ± 0.3832, KR: 0.2279 ± 0.2109). This suggests inability of host’s colon to productively use these SCFA. Levels of stool propionate appear to be linked to the recurrent environment (CC: 0.7620 ± 0.6562, I: 1.5162 ± 0.9189, IR: 0.6928 ± 0.5369, KR: 0.4490 ± 0.3406). Tryptophan catabolism has been linked to the CDI neutrophil response in mice. We detected decreased tryptophan in KR stool as well as lower numbers of circulating neutrophils (KR: 0.007 ± 0.007, CC: 0.0229 ± 0.0199, I: 0.0163 ± 0.0163, IR: 0.0246 ± 0.0201). This suggests altered host luminal metabolism can lead to biosystem changesConclusionCDI in the human biosystem is complex with contribution of host comorbidities and medications. The luminal interface between biome and host is the metabolome. NMR metabolomics of human in-patient stools can provide a more relevant understanding of what conditions are necessary for CDI, its clearance and recurrence. Defeat of this costly infection needs alternative approaches.Disclosures M. B. Yacyshyn, Merck: Grant Investigator, Research grant; B. Yacyshyn, Merck: Grant Investigator and Speaker’s Bureau, Research grant and Speaker honorarium

A thermo-sensitive OEGMA-based polymer: synthesis, characterization and interactions with surfactants in aqueous solutions with and without salt

The interactions between poly(2-(2-methoxyethoxy)ethyl methacrylate90-co-oligo(ethylene glycol) methacrylate10) (P(MEO2MA90-co-OEGMA10)) and sodium dodecyl sulfate (SDS) or dodecyltrimethyl ammonium bromide (DTAB) in aqueous solutions with and without salt are explored. The influence rule of surfactant on thermo-sensitive behavior of polymer and the corresponding mechanism is revealed. The results have suggested that both surfactants have moderate interactions with P(MEO2MA90-co-OEGMA10), which result in the formation of P(MEO2MA90-co-OEGMA10)/surfactant complexes. Meanwhile, the self-aggregation of polymer chains is hindered causing the lower critical solution temperatures (LCSTs) increase due to the electrostatic repulsion and “locking water” effect caused by surfactant head groups. Tetra-n-butylammonium bromide (Bu4NBr) and tetra-n-propylammonium bromide (Pr4NBr) can associate with SDS and form mixed micelles. Interestingly, the formed mixed micelles apt to attach on the polymer chain and the polymer-bound necklace-like structure forms in the ternary polymer/salt/surfactant system. The structure of the complexes formed in the ternary system is confirmed by 2D NOESY NMR and the interaction mode is proposed. The relations between LCST of different systems and surfactant concentrations are also established quantitatively.

Interaction of different statins with model membranes by NMR data

Hydroxy-methyl-glutaryl-coenzyme A (HMG-CoA) reductase inhibitors or statins reduce the amount of low-density lipoprotein (LDL) cholesterol, which is known as a well-established risk factor for atherosclerosis. Despite the fact that statins have a common pharmacologic target essential to sterol biosynthesis, their efficacy, safety, and potential non-LDL actions vary significantly for different statins. There is a hypothesis that pharmacological features of statins depend on their location in cell membrane, but to the present day there is a lack of information in literature on interactions of statins with the surface of the cell membrane in liquid media. The results of NMR experiments showed that all studied statins form intermolecular complexes with models of cell membranes (dodecylphosphocholine micelles) in water solution. Locations of pravastatin, simvastatin, fluvastatin and cerivastatin on model membranes were established by NOESY NMR data. Distinctions in their positions can explain differences in pharmacological properties of studied compounds.

Competitive and Synergistic Interactions between Polymer Micelles, Drugs, and Cyclodextrins: The Importance of Drug Solubilization Locus.

Polymeric micelles, in particular PEO-PPO-based Pluronic, have emerged as promising drug carriers, while cyclodextrins (CD), cyclic oligosaccharides with an apolar cavity, have long been used for their capacity to form inclusion complexes with drugs. Dimethylated β-cyclodextrin (DIMEB) has the capacity to fully breakup F127 Pluronic micelles, while this effect is substantially hindered if drugs are loaded within the micellar aggregates. Four drugs were studied at physiological temperature: lidocaine (LD), pentobarbital sodium salt (PB), sodium naproxen (NP), and sodium salicylate (SAL); higher temperatures shift the equilibrium toward higher drug partitioning and lower drug/CD binding compared to 25 °C ( Valero, M.; Dreiss, C. A. Growth, Shrinking, and Breaking of Pluronic Micelles in the Presence of Drugs and/or β-Cyclodextrin, a Study by Small-Angle Neutron Scattering and Fluorescence Spectroscopy . Langmuir 2010 , 26 , 10561 - 10571 ). The impact of drugs on micellar structure was characterized by small-angle neutron scattering (SANS), while their solubilization locus was revealed by 2D NOESY NMR. UV and fluorescence spectroscopy, Dynamic and Static Light Scattering were employed to measure a range of micellar properties and drug:CD interactions: binding constant, drug partitioning within the micelles, critical micellar concentration of the loaded micelles, aggregation number (Nagg). Critically, time-resolved SANS (TR-SANS) reveal that micellar breakup in the presence of drugs is substantially slower (100s of seconds) than for the free micelles (<100 ms) ( Valero, M.; Grillo, I.; Dreiss, C. A. Rupture of Pluronic Micelles by Di-Methylated β-Cyclodextrin Is Not Due to Polypseudorotaxane Formation . J. Phys. Chem. B 2012 , 116 , 1273 - 1281 ). These results combined together give new insights into the mechanisms of protection of the drugs against CD-induced micellar breakup. The outcomes are practical guidelines to improve the design of drug delivery systems as well as a better understanding of competitive assembly mechanisms leading to shape and function modulation.

Investigating Glycol-Split-Heparin-Derived Inhibitors of Heparanase: A Study of Synthetic Trisaccharides.

Heparanase is the only known endoglycosidase able to cleave heparan sulfate. Roneparstat and necuparanib, heparanase inhibitors obtained from heparin and currently being tested in man as a potential drugs against cancer, contain in their structure glycol-split uronic acid moieties probably responsible for their strong inhibitory activity. We describe here the total chemical synthesis of the trisaccharide GlcNS6S-GlcA-1,6anGlcNS (1) and its glycol-split (gs) counterpart GlcNS6S-gsGlcA-1,6anGlcNS (2) from glucose. As expected, in a heparanase inhibition assay, compound 2 is one order of magnitude more potent than 1. Using molecular modeling techniques we have created a 3D model of 1 and 2 that has been validated by NOESY NMR experiments. The pure synthetic oligosaccharides have allowed the first in depth study of the conformation of a glycol-split glucuronic acid. Introducing a glycol-split unit in the structure of 1 increases the conformational flexibility and shortens the distance between the two glucosamine motives, thus promoting interaction with heparanase. However, comparing the relative activities of 2 and roneparstat, we can conclude that the glycol-split motive is not the only determinant of the strong inhibitory effect of roneparstat.

The Dependency of Nematic and Twist-bend Mesophase Formation on Bend Angle.

We have prepared and studied a family of cyanobiphenyl dimers with varying linking groups with a view to exploring how molecular structure dictates the stability of the nematic and twist-bend nematic mesophases. Using molecular modelling and 1D 1H NOESY NMR spectroscopy, we determine the angle between the two aromatic core units for each dimer and find a strong dependency of the stability of both the nematic and twist-bend mesophases upon this angle, thereby satisfying earlier theoretical models.

Novel phenylenediamine bridged mixed ligands dimetallic square planner Pt(II) complex inhibits MMPs expression via p53 and caspase-dependent signaling and suppress cancer metastasis and invasion

Novel phenylenediamine bridged mixed ligands dimetallic square planner Pt(II) complex (L-Pt-Py) was synthesized from simple commercially available precursors in good yield and characterized by 1H, 13C, 2D NOESY NMR and high resolution mass spectrometry (HR-ESI-MS). The stability of L-Pt-Py was checked by 1H NMR in mixed DMSO-d6/D2O solvents. L-Pt-Py showed considerable in vitro cytotoxicity in lung (A549), breast (MCF-7) and liver (HepG2) cancer cell lines and strong in vivo growth inhibition in Escherichia coli (E. coli). These results were compared to the well-known market available platinum anticancer drug cisplatin. L-Pt-Py has strong ability to suppress the growth of multiple cancer cells. Mechanistically, it enhanced p53 protein expression and regulated p53-dependent genes expression such as p21, PUMA, MYC and hTERT. The TUNEL assay showed that L-Pt-Py induced cell death in cancer cells. Inhibition of caspase signaling with caspase inhibitor Z-VAD-FMK suggested that cell death induced by this complex was caspase-dependent. Importantly, L-Pt-Py has the ability to suppress the invasion and migration of human lung and luminal-like breast cancer cells. Similarly L-Pt-Py suppressed the expression of several matrix metalloproteinases (MMPs) such as MMP-1, MMP-2, MMP-3, MMP-7 and MMP-9 to inhibit lung and breast cancer cell metastasis. L-Pt-Py showed stronger inhibitory effects on bacterial growth and also resulted in filamentous morphology of bacterial cells. The gel electrophoresis study of DNA migration revealed the strong interaction of L-Pt-Py with DNA. Taken altogether, L-Pt-Py was highly stable and the in vitro and in vivo biological study results corroborated this complex to be effective anticancer agent.

High-Throughput Excipient Discovery Enables Oral Delivery of Poorly Soluble Pharmaceuticals.

Polymeric excipients are crucial ingredients in modern pills, increasing the therapeutic bioavailability, safety, stability, and accessibility of lifesaving products to combat diseases in developed and developing countries worldwide. Because many early-pipeline drugs are clinically intractable due to hydrophobicity and crystallinity, new solubilizing excipients can reposition successful and even failed compounds to more effective and inexpensive oral formulations. With assistance from high-throughput controlled polymerization and screening tools, we employed a strategic, molecular evolution approach to systematically modulate designer excipients based on the cyclic imide chemical groups of an important (yet relatively insoluble) drug phenytoin. In these acrylamide- and methacrylate-containing polymers, a synthon approach was employed: one monomer served as a precipitation inhibitor for phenytoin recrystallization, while the comonomer provided hydrophilicity. Systems that maintained drug supersaturation in amorphous solid dispersions were identified with molecular-level understanding of noncovalent interactions using NOESY and DOSY NMR spectroscopy. Poly(N-isopropylacrylamide-co-N,N-dimethylacrylamide) (poly(NIPAm-co-DMA)) at 70 mol % NIPAm exhibited the highest drug solubilization, in which phenytoin associated with inhibiting NIPAm units only with lowered diffusivity in solution. In vitro dissolution tests of select spray-dried dispersions corroborated the screening trends between polymer chemical composition and solubilization performance, where the best NIPAm/DMA polymer elevated the mean area-under-the-dissolution-curve by 21 times its crystalline state at 10 wt % drug loading. When administered to rats for pharmacokinetic evaluation, the same leading poly(NIPAm-co-DMA) formulation tripled the oral bioavailability compared to a leading commercial excipient, HPMCAS, and translated to a remarkable 23-fold improvement over crystalline phenytoin.

Encapsulation of Arenes within a Porous Molybdenum Oxide {Mo132 } Nanocapsule.

The use of confined space to modulate chemical reactivity and to sequester organic compounds spans significant disciplines in chemistry and biology. Here, the inclusion and assembly of arenes into a water-soluble porous metal oxide nanocapsule [{(MoVI )MoV5 O21 (H2 O)6 }12 {MoV2 O4 (CH3 COO)}30 ]42- (Mo132 ) is reported. The uptake of benzene, halobenzenes, alkylbenzenes, phenols, and other derivatives was studied by NMR, where it was possible to follow the encapsulation process from the outside of the capsule through its pores and then into the interior. The importance of size or shape of the arenes, and various intermolecular bond interactions contributed by the benzene substituent on the encapsulation process was studied, showing the importance of π-π stacking and CH-π interactions. Furthermore, by using NOESY, ROESY, and HOESY NMR techniques it was possible to understand the interaction of the encapsulated arenes and the acetate linkers or ligands that line the interior of the Mo132 capsule.

Patchy Supramolecular Bottle-Brushes Formed by Solution Self-Assembly of Bis(urea)s and Tris(urea)s Decorated by Two Incompatible Polymer Arms.

In an attempt to design urea-based Janus nanocylinders through a supramolecular approach, nonsymmetrical bis(urea)s and tris(urea)s decorated by two incompatible polymer arms, namely, poly(styrene) (PS) and poly(isobutylene) (PIB), were synthesized using rather straightforward organic and polymer chemistry techniques. Light scattering experiments revealed that these molecules self-assembled in cyclohexane by cooperative hydrogen bonds. The extent of self-assembly was limited for the bis(urea)s. On the contrary, reasonably anisotropic 1D structures (small nanocylinders) could be obtained with the tris(urea)s (Nagg ∼ 50) which developed six cooperative hydrogen bonds per molecule. (1)H transverse relaxation measurements and NOESY NMR experiments in cyclohexane revealed that perfect Janus nanocylinders with one face consisting of only PS and the other of PIB were not obtained. Nevertheless, phase segregation between the PS and PIB chains occurred to a large extent, resulting in patchy cylinders containing well separated domains of PIB and PS chains. Reasons for this behavior were proposed, paving the way to improve the proposed strategy toward true urea-based supramolecular Janus nanocylinders.

Ruthenium Lewis Acid‐Catalyzed Asymmetric Diels–Alder Reactions: Reverse‐Face Selectivity for α,β‐Unsaturated Aldehydes and Ketones

Acrolein, methacrolein, methyl vinyl ketone, ethyl vinyl ketone, 3‐methyl‐3‐en‐2‐one, and divinyl ketone were coordinated to a cationic cyclopentadienyl ruthenium(II) Lewis acid incorporating the electron‐poor bidentate BIPHOP–F ligand. Analysis by NOESY and ROESY NMR techniques allowed the determination of conformations of enals and enones present in solution in CD2Cl2. The results were compared to solid‐state structures and to the facial selectivities of catalytic asymmetric Diels–Alder reactions with cyclopentadiene. X‐Ray structures of four Ru‐enal and Ru‐enone complexes show the α,β‐unsaturated C=O compounds to adopt an anti‐s‐trans conformation. In solution, enals assume both anti‐s‐trans and anti‐s‐cis conformations. An additional conformation, syn‐s‐trans, is present in enone complexes. Enantioface selectivity in the cycloaddition reactions differs for enals and enones. Reaction products indicate enals to react exclusively in the anti‐s‐trans conformation, whereas with enones, the major product results from the syn‐s‐trans conformation. The alkene in s‐cis conformations, while present in solution, is shielded and cannot undergo cycloaddition. A syn‐s‐trans conformation is found in the solid state of the bulky 6,6‐dimethyl cyclohexanone‐Ru(II) complex. The X‐ray structure of divinyl ketone is unique in that the Ru(II) center binds the enone via a η2 bond to one of the alkene moieties. In solution, coordination to Ru–C=O oxygen is adopted. A comparison of facial preference is also made to the corresponding indenyl Lewis acids.

Small molecule probes finely differentiate between various ds- and ss-DNA and RNA by fluorescence, CD and NMR response

Two small molecules showed intriguing properties of analytical multipurpose probes, whereby one chromophore gives different signal for many different DNA/RNA by application of several highly sensitive spectroscopic methods. Dyes revealed pronounced fluorescence ratiomeric differentiation between ds-AU-RNA, AT-DNA and GC-DNA in approximate order 10:8:1. Particularly interesting, dyes showed specific fluorimetric response for poly rA even at 10-fold excess of any other ss-RNA, and moreover such emission selectivity is preserved in multicomponent ss-RNA mixtures. The dyes also showed specific chiral recognition of poly rU in respect to the other ss-RNA by induced CD (ICD) pattern in visible range (400–500 nm), which was attributed to the dye-side-chain contribution to binding (confirmed by absence of any ICD band for reference compound lacking side-chain). Most intriguingly, minor difference in the side-chain attached to dye chromophore resulted in opposite sign of dye-ICD pattern, whereby differences in NMR NOESY contacts and proton chemical shifts between two dye/oligo rU complexes combined with MD simulations and CD calculations attributed observed bisignate ICD to the dimeric dye aggregate within oligo rU.

Perfluoroalkyl Grignard Reagents: NMR Study of 1-Heptafluoropropylmagnesium Chloride in Solution

We report on the generation of a perfluoroalkyl Grignard reagent ((F)RMgX) by exchange reaction between a perfluoroalkyl iodide ((F)R-I) and a Grignard reagent (RMgX). (19)F NMR was applied to monitor the generation of n-C3F7MgCl. Additional NMR techniques, including (19)F COSY, NOESY, and pulsed gradient spin-echo (PGSE) diffusion NMR, were invoked to assign peaks observed in (19)F spectrum. Schlenk equilibrium was observed and was significantly influenced by solvent, diethyl ether, or THF.

One New Compound from the Extract of the Fungus Monascus purpureus BCRC 31499

A chemical investigation on the n-BuOH-soluble fraction of the 95% EtOH extract of red mold rice fermented with the fungus Monascus purpureus BCRC 31499 (Eurotiaceae) has resulted in the isolation of one new isochroman derivative, designated as monascupurpurin (1). The structure was elucidated as rel-(2S)-4,6-dimethyl-2-hexyl-7-O-α-L-rhamnosylisochroman-5-ol (1) on the basis of extensive 1D and 2D NMR techniques, including COSY, HMBC, HMQC, and NOESY correlations, as well as HR-ESI-MS analysis and comparison of the spectroscopic data with those reported for structurally related compounds. This is the first report on Monascus metabolites with an isochroman glycoside.