Search

An Unsteady Vortex Lattice Method is developed and validated. It is coupled with a decambering methodology to account for viscous effects on the aerodynamic coefficients. Two additional methodologies to select a unique solution when multiple solutions arise have been proposed. The transient nature of the aerodynamic loads of a suddenly moving wing at different angles of attack is examined. Sudden jumps are observed in the $$C_L(t)$$ at post-stall angles of attack. The jumps are followed by the presence of asymmetric solutions, which then decline with time and a change in the solution state. Higher angles of attack see an increasing number of jumps.

Recent biochemical and technical developments permit residue-specific solution NMR measurements of membrane protein (MP) dynamics in lipidic and chaperone-bound environments. This is possible by combinations of improved sample preparations with suitable NMR relaxation experiments to correlate protein function to backbone dynamics on timescales from picoseconds to seconds, even for large MP-lipid assemblies above 100 kDa in molecular mass. Here, we introduce the basic concepts of different NMR relaxation experiments, individually sensitive to specific timescales. We discuss the general limitations of detergent environments and highlight the importance for native-like environments when studying MPs. We then review three practical studies of fast- and slow-timescale MP dynamics in lipid environments, as well as in a natively unfolded, chaperone-bound state. These examples illustrate the new avenues solution NMR spectroscopy is taking to investigate MP dynamics in native-like environments with atomic resolution.

Conformational dynamics of GPCRs are central to their function but are difficult to explore at the atomic scale. Solution-state NMR has provided the major contribution in that area of study during the past decade, despite nonoptimized labeling schemes due to the use of insect cells and, to a lesser extent, yeast as the main expression hosts. Indeed, the most efficient isotope-labeling scheme ever to address energy landscape issues for large proteins or protein complexes relies on the use of 13CH3 probes immersed in a perdeuterated dipolar environment, which is essentially out of reach of eukaryotic expression systems. In contrast, although its contribution has been underestimated because of technical issues, Escherichia coli is by far the best-adapted host for such labeling. As it is now tightly controlled, we show in this review that bacterial expression can provide an NMR spectral resolution never achieved in the GPCR field.

Linear triplatinum complexes with 48e(-), [Pt3(μ-tdpmp)2(RNC)2](PF6)2 (R = 2,6-xylyl (3), (t)Bu (4)), were synthesized by using a branched tetraphosphine, tris(diphenylphosphinomethyl)phosphine (tdpmp), and characterized by crystallographic and spectroscopic analyses to show their novel dynamic behaviour in the solution state, in which the linear Pt3 unit was stabilized by two spinning tetraphosphine ligands.

We show that optical excitation of radical triplet pair systems can produce a fourfold NMR signal enhancement in solution, without the need for microwave pumping. Development of optical hyperpolarization methods will significantly impact all NMR user groups by boosting sensitivity and reducing signal averaging times.

Ionic liquid solutions of cellulose or dopes can be spun into Lyocell-type textile fibers by dry-jet wet spinning. An extruded dope is drawn over an air gap into water, where the water hydrates the ionic liquid and cellulose is regenerated. Spinnability studies have concentrated on the deformation and failure modes in the air gap and thus the rheology of the unhydrated spinning dope. Herein, a breach in the bath, another failure mode, is discussed. Dopes are prepared from the good spinning solvents NMMO·H2O and [DBNH]OAc and the poor spinning solvents [emim]OAc and [TMGH]OAc. The diffusion constants for water diffusing inwards and for ionic liquid diffusing outwards the emerging filament are measured offline. The resiliences and strengths of cellulose–ionic liquid solutions with different hydration stoichiometries are measured by means of rheometry. By calculating the diffusion dynamics, the resilience distribution of the forming filament is simulated. Gel strength distribution accounts for the tendency of [emim]OAc dopes to undergo a telescope-type breach, whereas the gelatinous solution state of [TMGH]OAc dopes accounts for their poor spinnability.

Ruthenium allenylidene complexes with carbon-rich polyaromatic moieties have been synthesized by using [RuCl(η5-C5H5)(PPh3)2] (η5-C5H5 = cyclopentadienyl) as a precursor and the propargyl alcohols 10-ethynyl-10-hydroxyanthracen-9-one (ACO), 13-ethynyl-13-hydroxypentacen-6-one (PCO), 1-phenyl-1-(pyren-1-yl)prop-2-yn-1-ol (PyrPh), 9-ethynyl-9H-fluoren-9-ol (FN) and 6-ethynyl-6H-benzo[cd]pyren-6-ol (BPyr) as ligands. The resulting cationic allenylidene complexes, [Ru(η5-C5H5)([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash](AO))(PPh3)2]PF6 (1), [Ru(η5-C5H5)([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash](PCO))(PPh3)2]PF6 (2), [Ru(η5-C5H5)([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash](PyrPh))(PPh3)2]PF6 (3), [Ru(η5-C5H5)([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash](FN))(PPh3)2]PF6 (4), and [Ru(η5-C5H5)([double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash](BPyr))(PPh3)2]PF6 (5) show interesting intermolecular π-interactions in the solid-state structure as well as solution state complexation with pyrene (documented by Job's plots experiments). CV data indicate possible Ru(II)/Ru(III) oxidation, as well as the potential reduction of the carbon-rich allenylidene moiety.

Addition of TMEDA to lithium allyl-1-naphthylamide in a 1 : 1 ratio afforded the novel amido lithium/lithiate complex, [Li(TMEDA)2][Li{N(1-naph)(CH2CH[double bond, length as m-dash]CH2)}2]. (7)Li NMR and computational calculations indicate this model to be representative of the solution state, with (1)H and (13)C NMR showing a 1,3-sigmatropic rearrangement. [Li{N(1-naph)(CH2CH[double bond, length as m-dash]CH2)}·Et2O]2, and [Li{N(1-naph) (CH2CH[double bond, length as m-dash]CH2)}·PMDETA] , are presented for comparison.

Characteristics of crystal quality, including crystal size distribution, size, morphology, polymorphism and chirality, have been established as important indicators of crystalline materials. There have been many attempts at controlling crystal quality during crystallization. Herein, this study summarizes crystal quality control by using temperature cycling during solution state crystallization. During crystallization, the temperature cycling is implemented through successive heating–cooling cycles for dissolution and recrystallization in crystal suspension. Therefore, the fines crystals or one species are expected to dissolve out completely during the heating period, and the remaining crystals or dominant species continuously grow or nucleate during the cooling period. When such temperature cycling is facilitated during crystallization, the characteristics of crystal quality, including crystal size distribution, size, morphology, polymorphism and chirality, are well managed. Furthermore, based on the basic principle of temperature cycling, the key parameters for controlling each characteristic of crystal quality are clearly elucidated during the process. Thus, this review provides qualitative insight into the general operation strategies and the principle of temperature cycling for crystal quality control during crystallization.

A biaryl-fused closo-o-carborane with a phenylthiophene moiety was synthesized and reacted with fluoride to obtain its nido-[C2B9] − species; the reaction with fluoride to obtain nido-[C2B9]− species was also performed for biphenyl- and bithiophene-fused o-carboranes, the synthesis of which we have previously reported. The structures and optoelectronic properties of the three carboranes and their nido-[C2B9]− species were experimentally and theoretically characterized. The nido-[C2B9]− species possessed high HOMO and LUMO energy levels because of the electron-rich anion species. They also displayed charge transfer (CT) transition bands, and efficient CT emissions were observed in the crystalline as well as solution state because of the shorter carbon–carbon bond length in the nido-carborane cage and suppression of the carbon–carbon bond vibration.

Luminescent properties of Sm(III), Eu(III), Tb(III) and Dy(III) complexes of three Schiff-base ligands viz. , H 2 L 1 , H 2 L 1 and H 2 L 3 [where H 2 L 1 = N,N’ -di-(4-decyloxysalicylidene)-1’,4’-diaminobutane; H 2 L 2 = N,N’ -di-(4-decyloxysalicylidene)- 2’,6’-diaminopyridine; and H 2 L 3 = N,N’ -di-(4-decyloxysalicylidene)-1’,3’-diaminobenzene] synthesized in our earlier work were investigated. The homo dinuclear lanthanide complexes were of the type, [Ln 2 (LH 2 ) 3 (NO 3 ) 4 ](NO 3 ) 2 . Luminescence analysis revealed that among the lanthanide complexes, only Sm(III) complex of H 2 L 1 was found to have displayed characteristic metal-centered emission (solution state) whereas Sm(III), Eu(III) and Tb(III) complexes of H 2 L 1 and Eu(III) and Tb(III) complexes of H 2 L 3 exhibited ligand-centered emissions. Journal of Institute of Science and Technology, 2014, 19(1): 19-24

Metformin hydrochloride is an oral antihyperglycemic drug used in the management of type-2 diabetes. Inclusion complexes were prepared between Metformin hydrochloride and alpha- cyclodextrin in solid and solution state. Inclusion complexes were characterised using UV-VIS, Fluorescence and FTIR Spectroscopic Studies. Phase solubility studies were carried out which determined the 1:1 stoichiometry for the formation of inclusion complexes.

Three 1,5-benzodiazepines viz., N 5-chloroacetyl-, N 5-piperazinoacetyl- and N 5-morpholinoacetyl-2,2,4-trimethyl-1H-1,5-benzodiazepines have been synthesized. The structural characterisation and the conformational preferences of the compounds have been carried out using IR, 1D and 2D NMR spectral data. The NMR spectral data show that the N-acetyltetrahydro-1,5-benzodiazepines prefer to exist in boat conformation with exo orientation of >C=O at N 5 position in the solution state. The X-ray crystal structure of N 5-morpholinoacetyl-2,2,4-trimethyl-1H-1,5-benzodiazepine also supports boat conformation in the solid state. The antimicrobial activity for N-acetyltetrahydro-1,5-benzodiazepines have been carried out. N-morpholinoacetyl-2,2,4-trimethyl-1H-1,5-benzodiazepine demonstrated better antibacterial and antifungal activities.

The intrinsic structural diversity of the nucleosides is one of the essential properties for their wide participation in myriads of chemical or biochemical processes. Two unique regio-isomeric Janus-type AT nucleosides with the 5′-deoxyribose attached on N1 or N3 position has been synthesized through Vorbrueggen or transglycosylation reactions. These two isomers display different supramolecular morphologies in solution state from their N8 glycosylated counterpart. The underneath structural details of the N3 glycosylated isomer were revealed by the single-crystal X-ray analysis. In addition to a novel base pair pattern was identified which is entirely different from the reverse Watson-Crick base pair adopted by its N8 isomer, an interesting water-filled columnar nanotuble-like structure was also found in its solid state. This study not only enriches the structural varieties of AT Janus-type nucleosides, but also provides specific information concerning the effect of the sugar glycosylation position on the properties of these new type of pyrimido[4,5-d]pyrimidine nucleosides.

A dicopper(II) complex can be covalently linked to palmitate/palmitoyl-oleoyl-phosphatidylcholine (PA/POPC) liposomes using the following one-pot strategy: preformed [Cu2(bpbp)(PA)](ClO4)2 (bpbp− = 2,6-bis((N,N′-bis(2-picolyl)amino)methyl)-4-tertbutylphenolato) was incorporated into POPC liposomes with a loading of up to 10 mol%. Despite its shape and charge, the decoration of PA/POPC liposomes with {Cu2(bpbp)}3+ did not disrupt the liposome structure; however, the mean liposome diameter increased from about 130 nm (0 mol% dicopper complex) to about 150 nm (10 mol% dicopper complex). Single-crystal X-ray structures furnish ‘snapshots’ of the pH-dependent solution state derivatives of {Cu2(bpbp)}3+, and model the structure of the [Cu2(bpbp)(PA)]2+ head group at the surface of the liposomes. An impressive plasticity in the intramolecular non-bonded Cu….Cu distance for these ions, ranging from 3 to 4 Å, in [Cu2(bpbp)OH]2+, [Cu2(bpbp)(OAc)(H2O)]2+ and [Cu2(bpbp)(H2O)2]3+ allows for their utility as labile reagents in water. Remarkably, the flexible dicopper site is selective for a single carboxylate ligand, so that [Cu2(bpbp)(PA)]2+ is favoured even in the presence of other chemically similar oxoanions, such as CO32 − , HCO3− , NO3− , ClO4− , ReO4− and CF3SO3− .

The number of protein sequences deriving from genome sequencing projects is outpacing our knowledge about the function of these proteins. With the gap between experimentally characterized and uncharacterized proteins continuing to widen, it is necessary to develop new computational methods and tools for protein structural information that is directly related to function. Nuclear magnetic resonance (NMR) provides powerful means to determine three-dimensional structures of proteins in the solution state. However, translation of the NMR spectral parameters to even low-resolution structural information such as protein class requires multiple time consuming steps. In this paper, we present an unorthodox method to predict the protein structural class directly by using the residue's averaged chemical shifts (ACS) based on machine learning algorithms. Experimental chemical shift information from 1491 proteins obtained from Biological Magnetic Resonance Bank (BMRB) and their respective protein structural classes derived from structural classification of proteins (SCOP) were used to construct a data set with 119 attributes and 5 different classes. Twenty four different classification schemes were evaluated using several performance measures. Overall the residue based ACS values can predict the protein structural classes with 80% accuracy measured by Matthew correlation coefficient. Specifically protein classes defined by mixed αβ or small proteins are classified with > 90% correlation. Our results indicate that this NMR-based method can be utilized as a low-resolution tool for protein structural class identification without any prior chemical shift assignments.

Hydrogen deuterium exchange mass spectrometry (HDX-MS) has become an increasingly routine technology for probing the solution structure and dynamics of proteins. HDX-MS measures the exchange of deuterium with the amide proton on the protein backbone chain. HDX-MS results can be used to aid in construct design for biophysical studies, to probe protein–ligand interactions and to characterize the dynamics of proteins. This digest highlights recent progress which makes this technology accessible and explores examples of HDX-MS in drug discovery and solution state structural biology.

Aggregation-induced emission (AIE), conceptually termed by Tang et al in 2001, refers to a unique phenomenon that a series of propeller-shaped conjugated molecules are weakly or non-emissive in solution state but highly luminescent in the aggregate state. Experimental and theoretical studies have rationalized the restriction of intramolecular motion (including rotation and vibration) as the main cause for the AIE effect. Exactly opposite to conventional fluorophores that suffer from the aggregation-caused quenching (ACQ) effect, the AIE luminogens (AIEgens) could perform best in the condensed phases and enable the molecule aggregation to play positive instead of negative roles in enhancing luminescence. Attracted by this intriguing phenomenon and the application implications, scientists worldwide have actively involved in this research and promoted the development of this area. As a result, tremendous AIEgens have been synthesized and applied in optoelectronic and biologic fields etc. The progresses on the AIE have been well summarized in several excellent reviews. However, the reviewed structures of AIEgens are mostly based on the hydrocarbon ones, such as tetraphenylethene (TPE), distyrylanthracene (DSA), triphenylethene, tetraphenyl-1,4-butadiene (TPBD). Herein, we mainly review the advance of heterocycle-based AIEgens containing silicon, nitrogen, sulfur, boron and phosphorus atoms etc. for the first time. The versatile properties, such as tunable emission color, good thermal and photo-stability, and the applications of these heterocycle-based AIEgens in organic light-emitting diodes, fluorescent sensors and cell imaging etc. were also briefly discussed.

Reaction of [Pd2(XylNC)6]X2 (X = PF6, BF4) with a linear tetraphosphine, meso-bis[(diphenylphosphinomethyl)phenylphosphino]methane (dpmppm), afforded binuclear Pd(I) complexes, [Pd2(μ-dpmppm)2]X2 ([2]X2), through an asymmetric dipalladium complex, [Pd2(μ-dpmppm)(XylNC)3](2+) ([1](2+)). Complex [2](2+) readily reacted with [Pd(0)(dba)2] (2 equiv) and an excess of isocyanide, RNC (R = 2,6-xylyl (Xyl), tert-butyl ((t)Bu)), to generate an equilibrium mixture of [Pd4(μ-dpmppm)2(RNC)2](2+) ([3'](2+)) + RNC ⇄ [Pd4(μ-dpmppm)2(RNC)3](2+) ([3](2+)), from which [Pd4(μ-dpmppm)2(XylNC)3](2+) ([3a](2+)) and [Pd4(μ-dpmppm)2((t)BuNC)2](2+) ([3b'](2+)) were isolated. Variable-temperature UV-vis and (31)P{(1)H} and (1)H NMR spectroscopic studies on the equilibrium mixtures demonstrated that the tetrapalladium complexes are quite fluxional in the solution state: the symmetric Pd4 complex [3b'](2+) predominantly existed at higher temperatures (0 °C), and the equilibrium shifted to the asymmetric Pd4 complex [3b](2+) at a low temperature (∼-30 °C). The binding constants were determined by UV-vis titration at 20 °C and revealed that XylNC is of higher affinity to the Pd4 core than (t)BuNC. In addition, both isocyanides exhibited higher affinity to the electron deficient [Pd4(μ-dpmppmF2)2(RNC)2](2+) ([3F'](2+)) than to [Pd4(μ-dpmppm)2(RNC)2](2+) ([3'](2+)) (dpmppmF2 = meso-bis[{di(3,5-difluorophenyl)phosphinomethyl}phenylphosphino]methane). When [2]X2 was treated with [Pd(0)(dba)2] (2 equiv) in the absence of RNC in acetonitrile, linearly ordered octapalladium chains, [Pd8(μ-dpmppm)4(CH3CN)2]X4 ([4]X4: X = PF6, BF4), were generated through a coupling of two {Pd4(μ-dpmppm)2}(2+) fragments. Complex [2](2+) was also proven to be a good precursor for Pd2M2 mixed-metal complexes, yielding [Pd2Cl(Cp*MCl) (Cp*MCl2)(μ-dpmppm)2](2+) (M = Rh ([5](2+)), Ir ([6](2+)), and [Au2Pd2Cl2(dpmppm-H)2](2+) ([7](2+)) by treatment with [Cp*MCl2]2 and [AuCl(PPh3)], respectively. Complex [7](2+) contains an unprecedented PC(sp(3))P pincer ligand with a PCPCPCP backbone, dpmppm-H of deprotonated dpmppm. The present results demonstrated that the binuclear Pd(I) complex [2](2+) was a quite useful starting material to extend the palladium chains and to construct Pd-involved heteromultinuclear systems.

Activated perethylated pillar[5]arene crystals show an unexpected alkane-shape- and -length-selective gate-opening behavior. Activated crystals were obtained upon removing solvents from perethylated pillar[5]arene crystals by heating. The activated crystals could quantitatively take up n-alkanes with carbon chains containing more than five carbon atoms as a consequence of their gate-opening pressure. As the chain length of the n-alkanes increased, the gate pressure decreased. A transformation into a herringbone structure was induced when n-hexane was used as a guest. By contrast, cyclic and branched alkanes were not taken up and could not induce a crystal transformation because they were too large to fit in the cavities of the pillar[5]arene. Alkane-shape-selective molecular recognition of pillar[5]arenes in the solution state was translated into the vapor/crystal state.

Backbone resonance assignment is a critical first step in the investigation of proteins by NMR. This is traditionally achieved with a standard set of experiments, most of which are not optimal for large proteins. Of these, HNCA is the most sensitive experiment that provides sequential correlations. However, this experiment suffers from chemical shift degeneracy problems during the assignment procedure. We present a strategy that increases the effective resolution of HNCA and enables near-complete resonance assignment using this single HNCA experiment. We utilize a combination of 2-13C and 3-13C pyruvate as the carbon source for isotope labeling, which suppresses the one bond (1Jαβ) coupling providing enhanced resolution for the Cα resonance and amino acid-specific peak shapes that arise from the residual coupling. Using this approach, we can obtain near-complete (>85%) backbone resonance assignment of a 42 kDa protein using a single HNCA experiment., Structure determination of large proteins by solution state NMR is challenging due to spectral overlap. Here the authors present a labeling strategy using 2-13C and 3-13C pyruvate as carbon source for E. coli, which increases the effective resolution of triple-resonance HNCA experiments and helps to overcome this problem.

Solid-state nuclear magnetic resonance (NMR) has recently emerged as a method of choice to study structural and dynamic properties of large biomolecular complexes at atomic resolution. Indeed, recent technological and methodological developments have enabled the study of ever more complex systems in the solid-state. However, to explore multicomponent protein complexes by NMR, specific labeling schemes need to be developed that are dependent on the biological question to be answered. We show here how to reconstitute an isotopically labeled protein within the unlabeled 50S or 70S ribosomal subunit. In particular, we focus on the 63-residue ribosomal protein L29 (~7 kDa), which is located at the exit of the tunnel of the large 50S ribosomal subunit (~1.5 MDa). The aim of this work is the preparation of a suitable sample to investigate allosteric conformational changes in a ribosomal protein that are induced by the nascent polypeptide chain and that trigger the interaction with different chaperones (e.g., trigger factor or SRP).

In this paper we have prepared a series of Ti(IV), Hf(IV) and Al(III) complexes based on bipyrrolidine salan pro-ligands. The Hf(IV) complexes have all been characterised in the solid-state, the chiral ligands coordinate to Hf(IV) in an α-cis manner whereas the meso ligand coordinates in a β-cis geometry. The Hf(IV) complexes are all active for the ROP of rac-lactide in the melt, with the fluxional meso complex affording a strong isotactic bias Pm = 0.84. As expected Hf(3)(OiPr)2 polymerised L-LA faster than rac-LA (kapp = 5.9 x 10-3 mins-1 vs 3.8 x 10-3 mins-1). For Ti(IV) complexes atactic PLA was formed. The salan pro-ligands have also been complexed to Al(III), with the complexes being characterised in the solid and solution state generating a series of novel Al-Me and Al-OiPr species. Al(1)(OiPr) was fluxional on the NMR timescale, whereas Al(3)(OiPr) was locked in solution with no exchange. Interestingly, the Al(III) complexes of 3H2 produce PLA with a very strong heterotactic bias Pr upto 0.87, whereas atactic PLA is produced with 1H2. For Al(3)(OiPr) a linear relationship is observed with Mn and conversion. Experiments with the addition of an equivalent of rac-LA to the selective initiators have also been performed and are discussed.

The signs of circularly polarised luminescence and circular dichroism of chiral biaryl fluorophores in the CHCl3-dissolved state (solution state) and the PMMA-film-dispersed state (solid state) were successfully controlled by modifying the internal axial chirality and the axial bonding position of the biaryl units.

Chiral ligand-modified polyoxometalates (POMs), (Bu4N)4[ﾎｳ-SiTi2W10O36(ﾎｼ-OH)2(ﾎｼ-BINOLate)], were successfully synthesized by the introduction of (R)- or (S)-BINOL into the dititanium-substituted tungstosilicate POM in an org. medium and characterized by x-ray crystallog., spectroscopy, and elemental analyses. These BINOL-modified POMs were stable in the soln. state and showed catalytic activity for asym. oxidn. of thioanisole. [on SciFinder(R)]

A family of electronically diverse pyridyl- and picolyl-substituted imidazolium salts have been prepared and coordinated to palladium in a single step, to deliver a variety of palladium(II)–N-heterocyclic carbene (NHC) complexes. Neutral Pd(NHC)X2, cationic [Pd(NHC)2X]X and dicationic [Pd(NHC)2]X2-type complexes have been isolated and fully characterised, with single-crystal X-ray analysis revealing a variety of coordination environments around the palladium centres. The pre-formed complexes have been employed in a model Suzuki–Miyaura cross-coupling reaction to yield a sterically congested tetra-ortho-substituted biaryl product, showcasing turnover numbers comparable to Pd-PEPPSI-IPr catalyst.

We presented a novel approach for pyrophosphate (PPi) sensing. Two tetraphenylethene (TPE)-functionalised pyridine salts (TPM and TPH) were designed and synthesized. Both of them exhibited weak emission in the solution state that originates from intramolecular charge transfer (ICT) from TPE to the pyridine; the addition of PPi into the TPM aqueous solution would enhance the fluorescence intensity, which eliminates the emission quenching effect of the iodide ion by the formation of PPi-sensor nanoparticles. The detection limit of TPM was determined to be as low as 133 nM. Meanwhile, a thin solid film of TPM that could detect PPi rapidly was conveniently prepared.

We report a facile synthesis of highly uniform poly(styrene sulfonic acid) microgels, which carry a strong polyelectrolyte group at every repeating unit. We demonstrate tuning of particle size, as well as particle softness, and show first solution state characterization.

A new kind of terpyridine-based Ca(2+) sensor TS was designed and studied based on the internal charge transfer (ICT). In the diluted solution state, TS sensed Ca(2+) and Mg(2+) ions among test ions via an "off-on" approach as seen from fluorescence spectra of test ions. Moreover, TS was able to form stable fluorescent gels in organic solvents accelerated by ultrasound, indicating the ultrasound responsive properties of TS molecules. The S-gel of TS could be successfully used to selectively recognize Ca(2+) through fluorescent emission color and morphological changes, which was different from that of the solution state. It was predicated that the competition between the self-assembly of TS molecules and the host–guest interaction of TS with Ca(2+) or Mg(2+) was responsible for the sensing properties. To the best of our knowledge, this is the first example that organogels could selectively sense Ca2+ ions.

Recently, a sequence with a set of non-equidistant π pulses, often referred to as Uhrig's Dynamic Decoupling (UDD) sequence has been proposed which is shown to be more efficient in suppressing the time dependent systematic sources of dephasing originating from a bosonic bath. This work aims to investigate the potential of such non-equidistant sequences for more accurate measurement of the transverse relaxation time (T2) in liquid state NMR. We have shown experimentally that the dynamic decoupling schemes can estimate T2 more accurately than the equidistant pulse sequence by suppressing the dephasing effects of the field noise in the solution state.

A wide range of spectroscopic and imaging techniques have been applied to silk, but the most detailed picture of the structure and dynamics of silk in molecular level has been revealed from NMR, using both solid and solution state measurements. In this review, ten NMR techniques from solution NMR to solid-state NMR used to study the structure of dynamics of silk materials and the obtained typical results were reviewed.

Monoclonal antibody (mAb)-based therapeutics often require high-concentration formulations. Unfortunately, highly concentrated antibody solutions often have biophysical properties that are disadvantageous for therapeutic development, such as high viscosity, solubility limitations, precipitation issues, or liquid-liquid phase separation. In this work, we present a computational rational design principle for improving the thermodynamic stability of mAb solutions through targeted point mutations. Two publicly available IgG1 monoclonal antibodies that exhibit high viscosity at high concentrations were used as model systems. Guided by a computationally efficient approach that combines molecular dynamics simulations with three-dimensional reference interaction site model theory, point mutations of charged residues were introduced in the variable Fv regions in such a manner that the hydration free energy was optimized. Two selected point mutants were then produced by transient expression and characterized experimentally. Both engineered mAbs have reduced viscosity at high concentration, less negative second virial coefficient, and improved solubility compared to the respective wild-types. The results obtained with the suggested straightforward design principle underline the relevance of solvation effects for understanding, and ultimately optimizing, the properties of highly concentrated mAb solutions, with possible implications also for other biomolecular systems.

Two highly versatile xanthene scaffolds containing pairs of heteroditopic ligands were found to be capable of accommodating a range of transition metal ions, including Au(I), Ir(I), Ir(III), Rh(I), and Ru(II) to generate an array of heterobimetallic complexes. The metal complexes were fully characterised and proved to be stable in the solid and solution state, with no observed metal–metal scrambling. Heterobimetallic complexes containing the Rh(I)/Ir(I) combinations were tested as catalysts for the two-step dihydroalkoxylation reaction of alkynediols and sequential hydroamination/hydrosilylation reaction of alkynamines.

Hydrogen peroxide (H2O2), an important reactive oxygen species (ROS), is related to the oxidative stress in organisms, and plays important roles in a variety of cellular activities as well. So it is of crucial importance to develop sensitive and accurate sensing strategies to detect H2O2 in biological systems. Herein, by taking advantage of the unique emission characteristics of aggregation induced emission (AIE) fluorogens, we proposed a non-enzymatic fluorescence platform for facile and sensitive detection of H2O2, both in solution state using fluorescence spectrometer and on paper-based sensor via visual inspection. Through the reaction between L-cysteine and H2O2, the fluorescence of TPE-M-L, an AIE fluorogen formed between maleimide-functionalized tetraphenylethene (TPE-M) and L-cysteine, is quenched, and highly sensitive non-enzymatic H2O2 assay is readily carried out. The limit of detection (LOD) of 10nM in solution state and 2.5μM on paper-based sensor were obtained for H2O2 detection, which were superior or comparable to those previously reported in literature. Moreover, by integrating glucose oxidase with the AIE fluorogen of TPE-M-L, highly sensitive and selective glucose detection was also conveniently achieved both in solution state and on paper-based sensor by the as-proposed strategy, with the LODs of 50nM in solution state and 10μM via visual observation, much better than those obtained by other fluorescence methods. The as-proposed sensing strategy was also successfully applied to assay glucose in human serum samples. Therefore, the paper-based fluorescence sensor exhibits the advantages of simple fabrication, high sensitivity and portability, and has great potential to be applied in on-site assay of H2O2 and glucose in real samples.

A [12]Cyclo-p-phenylene 9 composed of dinaphthofuran units and biphenyl units was synthesized through reductive elimination of the corresponding trinuclear complex by applying Yamago’s method. The X-ray crystallographic analyses of 9 revealed that it adopts a zigzag conformation in the solid state. The UV–vis and fluorescence measurements of compound 9 indicated that it also preferentially took a zigzag conformation in the solution state.

A 5-fold-interpenetrated zinc-based coordination polymer can discriminately detect aliphatic amines through a fluorescence “turn-on” method. This compound can sense aliphatic amines in the solid state, solution state, and vapor phase. Theoretical calculations revealed that the ground-state dipole moment of the corresponding amines guides the order of enhancement.

We propose a new approach for a totally organic, room-temperature phosphorescent system with a lifetime on the order of milliseconds, which is achieved by promotion of the one-dimensional chiral stacking of a simple, small fluorophore in a solution state. The versatility of this system is highlighted by its good applicability to the fabrication of a phosphorescent polymer film. This paper demonstrates the first example of a room-temperature phosphorescent polymer film prepared with our methodology.

In order to increase the sensitivity of a polydiacetylene (PDA) sensor, PDA, and poly(sodium 4-styrene-sulfonate) (PSS) were alternately stacked to form a layer-by-layer (LBL) film on the quartz. In this study, N-(2-aminoethyl)pentacosa-10,12-diynamide (AEPCDA) was used as a constituent of the PDA and n-butylamine was used as a target compound. The formed-film sensor showed higher sensitivity than the vesicle solution. There was a large difference in sensitivity depending on the method used to form the LBL film. Unlike the vesicle solution state, the formed-film sensor exhibited excellent reversibility in the color change caused by heat. The LBL film formed worked very well as a sensor that detects the actual gas, n-butyl amine, showing its potential for practical applications. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44997.

The synthesis and solid state structures of homo- and heteroleptic Zr and Ti complexes of 2-(diphenylphosphino)pyrrolide (NP) are reported. The homoleptic Zr(NP)4 (1) and Ti(NP)4 (2) are 8-coordinate in the solid state, and both show extremely long M–P bonds of approximately 2.9 A. In solution, the phosphine ligands in all complexes are labile: in the titanium complexes phosphine dissociation is rapid at room temperature and equilibrates all phosphines into a single 31P resonance, whereas in the Zr complex 1 dissociation is slower and full equilibration does not occur until 90 °C. The potential to utilize these novel complexes as metalloligands toward other transition metals is discussed.

The synthesis, structures, and emission properties of vaulted trans-bis(salicylaldiminato)platinum(II) complexes 1 with diethylamino functionalities are described and compared with the non-substituted analogues. The amino substitution provides an improvement of the linker dependence both for the color change of the trans-bis(salicylaldiminato)platinum(II) platform in the glass state and for the acid-induced emission enhancement in the solution state. The linker dependence of the crystalline-state emission intensity changes with the amino functionality, which leads to intense emission of the vaulted crystals with low structural dependence. Single-crystal X-ray diffraction studies and DFT calculations revealed that the unique photophysical properties arising from the amino functionality are attributable to enhanced planarity and self-constraint of the coordination platform, which is due to their strong contribution to d–π conjugation and intermolecular hydrogen bonding.

Tris(2-aminoethyl)amine (TREN) based pentafluorophenyl urea and 4-cyanophenyl thiourea receptors have shown encapsulation of oxalate (\(\mathrm {C}_{{2}}\mathrm {O}_{{4}}^{{2-}})\) in semi-aqueous environment. A single crystal X-ray study shows trapping of planar conformer of \(\mathrm {C}_{{2}}\mathrm {O}_{{4}}^{{2-}}\) in both the cases. Further solution state binding of \(\mathrm {C}_{{2}}\mathrm {O}_{{4}}^{{2-}}\) is probed by 1H-NMR titration study in semi-aqueous solvent.

Polyesters are biodegradable analogues of polypeptides, but their biochemical applications have been hampered by the lack of a method to analyze polyester conformation in a solution state. We have demonstrated that vibrational circular dichroism (VCD) spectroscopy can conveniently and accurately elucidate the conformation of polyesters through the studies on poly(l-lactic acid) (PLLA), PLLA-amylose complex, and oligo(l-lactic acid). The analysis of VCD exciton couplet of these molecules has clarified the stable left-handed helical structure of PLLA, while density functional theory calculations of oligo(l-lactic acid) have revealed its detailed structural nature.

Systematic structural perturbation has been used to fine-tune and understand the luminescence properties of three new 1,8-naphthalimides (NPIs) in solution and aggregates. The NPIs show blue emission in the solution state and their fluorescence quantum yields are dependent upon their molecular rigidity. In concentrated solutions of the NPIs, intermolecular interactions were found to quench the fluorescence due to the formation of excimers. In contrast, upon aggregation (in THF/H2O mixtures), the NPIs show aggregation-induced emission enhancement (AIEE). The NPIs also show moderately high solid-state emission quantum yields (ca. 10-12.7 %). The AIEE behaviour of the NPIs depends on their molecular rigidity and the nature of their intermolecular interactions. The NPIs 1-3 show different extents of intermolecular (pi-pi and C-H center dot center dot center dot O) interactions in their solid-state crystal structures depending on their substituents. Detailed photophysical, computational and structural investigations suggest that an optimal balance of structural flexibility and intermolecular communication is necessary for achieving AIEE characteristics in these NPIs.

The biochemical processes of living cells involve a numerous series of reactions that work with exceptional specificity and efficiency. The tight control of this intricate reaction network stems from the architecture of the proteins that drive the chemical reactions and mediate protein–protein interactions. Indeed, the structure of these proteins will determine both their function and interaction partners. A detailed understanding of the proximity and orientation of pivotal functional groups can reveal the molecular mechanistic basis for the activity of a protein. Together with X-ray crystallography and electron microscopy, NMR spectroscopy plays an important role in solving three-dimensional structures of proteins at atomic resolution. In the challenging field of membrane proteins, retinal-binding proteins are often employed as model systems and prototypes to develop biophysical techniques for the study of structural and functional mechanistic aspects. The recent determination of two 3D structures of seven-helical trans-membrane retinal proteins by solution-state NMR spectroscopy highlights the potential of solution NMR techniques in contributing to our understanding of membrane proteins. This review summarizes the multiple strategies available for expression of isotopically labeled membrane proteins. Different environments for mimicking lipid bilayers will be presented, along with the most important NMR methods and labeling schemes used to generate high-quality NMR spectra. The article concludes with an overview of types of conformational restraints used for generation of high-resolution structures of membrane proteins. This article is part of a Special Issue entitled: Retinal Proteins — You can teach an old dog new tricks.

Study of the interaction between prion proteins and humic and fifulvic substances by NMR spectroscopy

A new strategy was developed to controllably grow the organic crystals of two Troger's base analogues 2,8-(6H,12H-5,11-methanodibenzo[b,f]diazocineylene)-di(p-ethenylpyridine) (TBPP) and 5,6,11,12-tetrahydro-2,8-dimethylphenhomazine-di(p-ethenyl-N-pyridine) (PHZPP) from the same reactant TBPP. By adjusting the solvent conditions of the solvothermal system, TBPP crystals can be grown; on the other hand, from DMF-H2O systems with appropriate ratios, the methylene bridge of the Troger's base would be removed and PHZPP crystalized. It is a good method to synthesize PHZPP from Troger's base precursor under more moderate and greener solvothermal conditions. Furthermore, the different aggregation of TBPP and PHZPP crystals which may originate from the small differences in molecular structures resulted in distinct crystal fluorescent properties. The relationship between aggregate packing and photophysical properties was studied. In addition, PHZPP can be used as a pH probe for detecting H+ in solution state.

Unlike in the solution state, the first circularly polarized luminescence (CPL) property of the axially chiral binaphthyl fluorophore bearing two fluorescent terthiophene units was successfully obs...

A series of thieno[3,2-c]pyrans were designed and synthesized by L-proline catalyzed reaction of 6-aryl/5,6-diaryl-4-methylthio-2H-pyrane-2-one-3-carbonitriles or 4-(methylthio)-2-oxo-5,6-dihydro-2H-benzo[h]chromene-3-carbonitrile and methylthioglycolate in good yields. These thieno[3,2-c]pyrans exhibit substituent dependent fluorescence. The 6-aryl-thieno[3,2-c]pyrans 3a–3e exhibit high fluorescence quantum yields (95%) with large Stokes shifts, whereas the 6,7-di-substituted-thieno[3,2-c]pyrans 3f–3h show poor fluorescence in solution and exhibit an aggregation-induced emission (AIE). Interestingly, fused 6,7-di-substituted-thieno[3,2-c]pyran is highly fluorescent in the solution state, which reveals that restricted intramolecular rotation is the cause for AIE in 3f–3h.