Hydroxyl group recognition by hydrogen-bonding donor and acceptor sites embedded in a layered metal-organic framework

One of the dominant types of interactions between host and guest molecules is hydrogen-bonding, and these interactions can work selectively for a guest molecule. Here, we demonstrate a metal-organic framework (MOF) having both hydrogen-bonding donor and acceptor sites that are quite effective for selective sorption. The MOF selectively interacts with hydroxylic guests in contrast to aprotic hydrogen-bonding guests and shows a sorption selectivity for protic H(2)O, MeOH, and EtOH guests. Notably, this is the first compound that shows complete selectivity in adsorption not for MeCN and MeCHO but for EtOH, which has similar fundamental properties except for its proticity.     

Precise control and consecutive modulation of spin transition temperature using chemical migration in porous coordination polymers

Precise control of spin transition temperature (T(c)) is one of the most important challenges in molecular magnetism. A Hofmann-type porous coordination polymer {Fe(pz)[Pt(II)(CN)(4)]} (1; pz = pyrazine) exhibited cooperative spin transition near room temperature (T(c)(up) = 304 K and T(c)(down) = 284 K) and its iodine adduct {Fe(pz)[Pt(II/IV)(CN)(4)(I)]} (1-I), prepared by oxidative addition of iodine to the open metal sites of Pt(II), raised the T(c) by 100 K. DSC and microscopic Raman spectra of a solid mixture of 1-I and 1 revealed that iodine migrated from 1-I to 1 through the grain boundary after heating above 398 K. We have succeeded in precisely controlling the iodine content of {Fe(pz)[Pt(CN)(4)(I)(n)]} (1-In; n = 0.0-1.0), which resulted in consecutive modulation of T(c) in the range 300-400 K while maintaining the hysteresis width. Furthermore, it was demonstrated that iodine migration in the solid mixture was triggered by the spin transition of 1-I. The magnetically bistable porous framework decorating guest interactive open-metal-site in the pore surface makes it possible to modulate T(c) ad arbitrium through unique postsynthetic method using iodine migration.     

Aptamer-barcode based immunoassay for the instantaneous derivatization chemiluminescence detection of IgE coupled to magnetic beads

We report on a highly sensitive aptameric assay system for the determination of IgE, where a special chemiluminescence (CL) reagent, 3,4,5-trimethoxylphenylglyoxal (TMPG), acts as the signaling molecule and polystyrene beads as the amplification platform. Briefly, a "sandwich-type" detection strategy is employed in our design, where magnetic beads functionalized with a capture antibody were reacted with the target protein IgE, and then sandwiched with the aptamer-barcodes which were prepared by assembling polystyrene beads with IgE aptamer. The target immunoreaction event could be sensitively detected via an instantaneous derivatization reaction between TMPG and the guanine (G) nucleotides within the aptamer-barcodes to form an unstable CL intermediate for the generation of light. Further signal amplification is achieved by extending the G nucleotide-rich domain on the aptamer backbone for second amplification. Such simple amplified CL transduction allows the detection of IgE down to the 4.6 pM level, which is better than most previous aptameric methods for IgE detection. This new protocol also provides a good capability in discriminating IgE from nontarget proteins such as IgG, IgA, IgM, interferon and thrombin. The practical application of the proposed aptamer-barcode based immunoassay was successfully carried out for the determination of IgE in 20 human serum samples. It is straightforward to adapt this strategy to detect a spectrum of other proteins by using different aptamers, thus this method may offer a new direction in designing high-performance CL aptasensors for early diagnoses of diseases.     

Efficient synthesis of [¹¹C]ramelteon as a positron emission tomography probe for imaging melatonin receptors involved in circadian rhythms

Ramelteon (TAK-375) is a novel melatonin receptor agonist that is used for clinical treatment of insomnia. The present report describes radiolabeling of ramelteon with the short-lived positron-emitter 11C (T(1/2)=20.4 min) by 2 methods. One method was [11C]methylation of an acetoamide precursor and the other was [11C]acylation of the corresponding amine precursor. First, [11C]methylation method showed the low reproducibility together with the production of many kinds of side products from which the [11C-methyl]Ramelteon was separated with chemical purity of <28% and radiochemical purity of >98%. Whereas, the [11C]acylation method showed high efficiency and reproducibility with a good radiochemical yield (22-43%, decay corrected), high chemical and radiochemical purities (>99% each), and high specific activity (43-162 GBq/μmol) (n=5) after HPLC purification. [11C]Ramelteon is a potential positron emission tomography (PET) probe for imaging the melatonin receptor.     

A theoretical and experimental study on translational and internal energies of H2O and OH from the 157 nm irradiation of amorphous solid water at 90 K

The photodesorption of H(2)O in its vibrational ground state, and of OH radicals in their ground and first excited vibrational states, following 157 nm photoexcitation of amorphous solid water has been studied using molecular dynamics simulations and detected experimentally by resonance-enhanced multiphoton ionization techniques. There is good agreement between the simulated and measured energy distributions. In addition, signals of H(+) and OH(+) were detected in the experiments. These are inferred to originate from vibrationally excited H(2)O molecules that are ejected from the surface by two distinct mechanisms: a direct desorption mechanism and desorption induced by secondary recombination of photoproducts at the ice surface. This is the first reported experimental evidence of photodesorption of vibrationally excited H(2)O molecules from water ice.     

Conformational reduction of DOPA in the gas phase studied by laser desorption supersonic jet laser spectroscopy

The conformational reduction in catecholamine neurotransmitters was studied by resonance enhanced multi photon ionization (REMPI), ultraviolet-ultraviolet (UV-UV) hole burning and infrared (IR) dip spectroscopy with applying a laser desorption supersonic jet technique to DOPA, which is one of the catecholamine neurotransmitters and has one more phenolic OH group than tyrosine. It is concluded that DOPA has a single observable conformer in the gas phase at low temperature. Quantum chemical calculations at several levels with or without the dispersion correction were also carried out to study stable conformations. From the comparison between the computational IR spectra and the experimental ones, the most stable structure was determined. It is strongly suggested that the conformational reduction is caused by electrostatic interactions, such as a dipole-dipole interaction, between the chain and OH groups.     

Controlled kinetics of non-enzymatic chemiluminescence reactions for simple imaging of DNA and protein

A robust and sensitive non-enzymatic chemiluminescence (CL) imaging method is presented. In the method a fast-emitting CL reaction is tuned to furnish a slower-emitting reaction suitable for simple CL imaging. Typically, non-enzymatic CL reactions between luminol or fluorescein and oxygen species generated by KCN as catalyst, were rather fast and unsuitable for CL imaging; the speed of the reactions could, however, be reduced substantially by changing KCN for CH(3)CN or benzonitrile. Light emission from the tuned CL reaction was intense and long-lived, and even with a simple arrangement high sensitivity could be achieved. The maximum CL peak was reached after approximately 1.5 min in the presence of 25% acetonitrile, and as little as 16 fmol commercial isoluminol-labeled streptavidin was detected and visualized on either microplate or membrane. The approach was further illustrated by imaging of DNA on a membrane and of antibody on a microplate by use of biotin-streptavidin chemistry. Overall, this simple, economical, and sensitive CL imaging system is expected to be very useful in biochemical analysis, and greatly complements currently used enzyme-based CL imaging methods, especially in routine applications.     

Spatial coherence of laser light propagating in an optical fibre

The modulus of the complex degree of spatial coherence at the exit face of an optical fibre is determined for a quasi-monochromatic, spatially coherent source. It is found that the contribution of the cross-terms between many modes to the formulus of pointwise correlation is negligible for a highly multimode fibre in which even and odd modes are equally excited, although care must be taken when even or odd modes only are selectively excited in the waveguide. Experimental results obtained by using a Koesters prism in the wavefront reversing interferometer are also presented for a graded-index multimode fibre and a quasi-single mode fibre. Modal contents of the propagating field in the optical fibre can be successfully determined, provided that the coherence time of a quasi-monochromatic source and the path difference of the wavefront reversing system are knowna priori.     

Vibrational OH-stretching overtone spectroscopy of jet-cooled resorcinol and hydroquinone rotamers

We have measured the OH-stretching fundamental and overtone spectra of resorcinol and hydroquinone in a supersonic jet using nonresonant ionization detected infrared/near-infrared spectroscopy. Anharmonic oscillator local mode calculations of the OH-stretching frequencies and intensities and Boltzmann populations of the stable rotamers have been calculated at the B3LYP/6-311++G(3df,2pd) level to help interpret the observed spectra. Resorcinol has three stable rotamers and in the recorded second and third OH-stretching overtone spectra there is evidence of two distinguishable rotamers. Hydroquinone has two stable rotamers; however, the OH-stretching oscillators of each rotamer are so similar in nature that even up to the fourth OH-stretching overtone the transitions coincide. These results place a limit on the ability of the jet-cooled overtone spectroscopy technique to distinguish between rotamers.