O2 Binding and Dissociation and Ligand Exchange Reaction of O2 with CO in Polymer Composite Films of Hemoglobin

A polymer composite film of hemoglobin (Hb–polymer film) was prepared by the casting of an Hb–polymer mixed solution (weight ratio of Hb to polymer is 1 to 1). The percentages of O₂ and CO saturation of the Hb–dextran film were 46% and 70%, respectively. In the Hb solution, 100% saturation was observed for both ligands, and a humidified Hb–dextran film also showed 100% saturation. Water molecules would provide flexibility to the matrix polymer and promote a structural change in the Hb from a tense state (T) to a relaxed state (R). Thus the ligand binding to the Hb in the polymer films was strongly affected by the degree of interaction of Hb with the matrix polymers and the physical properties of the polymers. Inositol hexaphosphate (IHP) worked as an allosteric effector even in the solid polymer film and lowered the oxygen affinity of Hb. The O₂ transport through an Hb–polyethyleneimine (PEI) film with IHP showed the facilitated O₂ transport in comparison with the film without IHP because of the high dissociation rate of O₂ from Hb with IHP. © 1997 John Wiley & Sons, Ltd.     

Aptamer-modified DNA tetrahedra-gated metal–organic framework nanoparticle carriers for enhanced chemotherapy or photodynamic therapy

UiO-66 metal–organic framework nanoparticles (NMOFs) gated by aptamer-functionalized DNA tetrahedra provide superior biomarker-responsive hybrid nano-carriers for biomedical applications. Hybrid nano-carriers consisting of ATP-aptamer or VEGF-aptamer functionalized tetrahedra-gated NMOFs are loaded with the chemotherapeutic drug, doxorubicin (DOX). In the presence of ATP or VEGF, both abundant in cancer cells, the tetrahedra-gated NMOFs are unlocked to release the drug. Enhanced and selective permeation of the DOX-loaded ATP/VEGF-responsive tetrahedra-gated NMOFs into MDA-MB-231 breast cancer cells as compared to the reference ATP/VEGF-responsive duplex-gated NMOFs or non-malignant MCF-10A epithelial breast cells is observed. This results in enhanced and selective cytotoxicity of the tetrahedra-gated DOX-loaded NMOFs toward the malignant cells. Additional nano-carriers, consisting of photosensitizer Zn(ii) protoporphyrin IX (Zn(ii)-PPIX)-loaded VEGF-responsive tetrahedra-gated NMOFs, are introduced. The VEGF-triggered unlocking of the NMOFs yields separated G-quadruplex-VEGF aptamer complexes conjugated to the tetrahedra, resulting in the release of loaded Zn(ii)-PPIX. Association of the released Zn(ii)-PPIX to the G-quadruplex structures generates highly fluorescent supramolecular Zn(ii)-PPIX/G-quadruplex VEGF aptamer-tetrahedra structures. The efficient and selective generation of the highly fluorescent Zn(ii)-PPIX/G-quadruplex VEGF aptamer-tetrahedra nanostructures in malignant cells allows the light-induced photosensitized generation of reactive oxygen species (ROS), leading to high-efficacy PDT treatment of the malignant cells.

UiO-66 metal–organic framework nanoparticles (NMOFs) gated by aptamer-functionalized DNA tetrahedra provide superior biomarker-responsive hybrid nano-carriers for biomedical applications.     

An intrinsic synthesis parameter governing the crystallization of silico(zinco)aluminophosphate molecular sieves

One of the most fundamental but yet unanswered questions in the synthesis of zeolites and zeolite-like materials is whether or not any parameter controlling the microporosity of the crystallized product from synthesis mixtures with feasible chemical compositions exists. Here we report that an experimentally optimized parameter (ca. 3.3 ≤ MOH/P₂O₅ ≤ 5.3, where M is alkali metal ions) is the criterion bringing about the successful formation of various high-charge-density silicoaluminophosphate (SAPO) and zincoaluminophosphate (ZnAPO) molecular sieves, without the aid of organic structure-directing agents. The materials obtained using this empirical concept include SAPO molecular sieves with CHA and LTA topologies, as well as a SAPO FAU/EMT intergrowth, and ZnAPO ones with CZP and SOD topologies. This study demonstrates the existence of an essential factor determining not only phase selectivity but also microporosity (0.3–2 nm) in the synthesis of zeotypes with charged frameworks which may offer interesting opportunities for more efficiently producing novel zeolite structures and/or compositions.

The existence of an essential parameter (ca. 3.3 ≤ MOH/P₂O₅ ≤ 5.3, where M is alkali metal ions used as structure-directing agents) determining phase selectivity and microporosity in the synthesis of zeotypes with charged frameworks is demonstrated.     

Species Differences in Metabolism of Soluble Epoxide Hydrolase Inhibitor,EC1728, Highlight the Importance of Clinically Relevant Screening Mechanisms in Drug Development

There are few novel therapeutic options available for companion animals, and medications rely heavily on repurposed drugs developed for other species. Considering the diversity of species and breeds in companion animal medicine, comprehensive PK exposures in the companion animal patient is often lacking. The purpose of this paper was to assess the pharmacokinetics after oral and intravenous dosing in domesticated animal species (dogs, cats, and horses) of a novel soluble epoxide hydrolase inhibitor, EC1728, being developed for the treatment of pain in animals. Results: Intravenous and oral administration revealed that bioavailability was similar for dogs, and horses (42 and 50% F) but lower in mice and cats (34 and 8%, respectively). Additionally, clearance was similar between cats and mice, but >2× faster in cats vs. dogs and horses. Efficacy with EC1728 has been demonstrated in mice, dogs, and horses, and despite the rapid clearance of EC1728 in cats, analgesic efficacy was demonstrated in an acute pain model after intravenous but not oral dosing. Conclusion: These results demonstrate that exposures across species can vary, and investigation of therapeutic exposures in target species is needed to provide adequate care that addresses efficacy and avoids toxicity.     

Analysis of transient membrane protein interactions by single-molecule diffusional mobility shift assay

Various repertoires of membrane protein interactions determine cellular responses to diverse environments around cells dynamically in space and time. Current assays, however, have limitations in unraveling these interactions in the physiological states in a living cell due to the lack of capability to probe the transient nature of these interactions on the crowded membrane. Here, we present a simple and robust assay that enables the investigation of transient protein interactions in living cells by using the single-molecule diffusional mobility shift assay (smDIMSA). Utilizing smDIMSA, we uncovered the interaction profile of EGFR with various membrane proteins and demonstrated the promiscuity of these interactions depending on the cancer cell line. The transient interaction profile obtained by smDIMSA will provide critical information to comprehend the crosstalk among various receptors on the plasma membrane.Subject terms: Fluorescence imaging, Super-resolution microscopy, Single-molecule biophysics     

Solid-phase microextraction coupled with high-performance liquid chromatography for the determination of phenylurea herbicides in aqueous samples

Solid-phase microextraction coupled with high-performance liquid chromatography was successfully applied to the analysis of nine phenylurea herbicides (metoxuron, monuron, chlorotoluron, isoproturon, monolinuron, metobromuron, buturon, linuron, and chlorbromuron). Polydimethylsiloxane-divinylbenzene (PDMS-DVB, 60 microm) and Carbowax-templated resin (CW-TPR, 50 microm) fibers were selected from four commercial fibers for further study because of their better extraction efficiencies. The parameters of the desorption procedure were studied and optimized. The effects of the properties of analytes and fiber coatings, carryover, duration and temperature of absorption, pH, organic solvent and ionic strength of samples were also investigated. External calibration with an aqueous standard can be used for the analysis of environmental samples (lake water) using either PDMS-DVB or CW-TPR fibers. Good precisions (1.0-5.9%) are achieved for this method, and the detection limits are at the level of 0.5-5.1 ng/ml.     

Efficient excitation energy transfer in long meso-meso linked Zn(II) porphyrin arrays bearing a 5,15-bisphenylethynylated Zn(II) porphyrin acceptor

Electronically coupled porphyrin arrays are suitable for artificial light harvesting antenna in light of a large absorption cross-section and fast excitation energy transfer (EET). Along this line, an artificial energy transfer model system has been synthesized, comprising of an energy donating meso-meso linked Zn(II) porphyrin array and an energy accepting 5,15-bisphenylethynylated Zn(II) porphyrin linked via a 1,4-phenylene spacer. This includes an increasing number of porphyrins in the meso-meso linked Zn(II) porphyrin array, 1, 2, 3, 6, 12, and 24 (Z1A, Z2A, Z3A, Z6A, Z12A, and Z24A). The intramolecular singlet-singlet EET processes have been examined by means of the steady-state and time-resolved spectroscopic techniques. The steady-state fluorescence comes only from the acceptor moiety in Z1A-Z12A, indicating nearly the quantitative EET. In Z24A that has a molecular length of ca. 217 A, the fluorescence comes largely from the acceptor moiety but partly from the long donor array, indicating that the intramolecular EET is not quantitative. The transient absorption spectroscopy has provided the EET rates in real time scale: (2.5 ps)(-1) for Z1A, (3.3 ps)(-1) for Z2A, (5.5 ps)(-1) for Z3A, (21 ps)(-1) for Z6A, (63 ps)(-1) for Z12A, and (108 ps)(-1) for Z24A. These results have been well explained by a revised F?rster equation (Sumi formula), which takes into account an exciton extending coherently over several porphyrin pigments in the donor array, whose length is not much shorter than the average donor-acceptor distance. Advantages of such strongly coupled porphyrin arrays in light harvesting and transmission are emphasized in terms of fast EET and a large absorption cross-section for incident light.     

Depigmenting activity and low cytotoxicity of alkoxy benzoates or alkoxy cinnamte in cultured melanocytes

To obtain effective and safe topical depigmenting agents, we synthesized hydroxybenzoates, alkoxybenzoates, and 3,4,5-trimethoxycinnamate containing a thymol moiety and screened then for high-level inhibitory activity against melanin synthesis in cultured melanocytes. Eight compounds were tested for their depigmenting effect and cytotoxicity using a murine melanocyte cell line. We found that 3,4,5-trialkoxybenzoates and 3,4,5-trimethoxycinnamate, synthesized by conjugating 3,4,5-trialkoxybenzoic acids and 3,4,5-trimethoxycinnmic acid with thymol, showed a potent depigmenting effect and low cytotoxicity. Compound 4h, 5-methyl-2-(methylethyl)phenyl (2E)-3-(3,4,5-trimethoxyphenyl)prop-2-enoate, showed the most potent depigmenting effect (IC50=10 microM) with low cytotoxicity (IC50=200 microM).     

Micropatterning of polymer thin films with pH-sensitive and cross-linkable hydrogen-bonded polyelectrolyte multilayers

Polyelectrolyte multilayers of poly(acrylic acid) (PAA) and polyacrylamide (PAAm) were prepared via hydrogen-bonding interactions. These multilayers as assembled were stable at low pH but dissolved quickly in neutral pH water. We developed methods for stabilizing these multilayers to high pH through cross-linking by heating or UV-irradiation. Thermal treatment of the multilayers, which resulted in a partial imidization between carboxylic acid and amide groups, gave the multilayer good stability at high pH. In addition, we introduced photoreactive groups in the multilayer, which rendered the film insoluble after UV irradiation. Using these selective stabilization approaches, we have succeeded in micropatterning these films by ink-jet printing and photolithography to create subtractive patterns.     

Efficient total synthesis of pulchellalactam,a CD45 protein tyrosine phosphatase inhibitor

A new approach to a CD45 protein tyrosine phosphatase inhibitor, pulchellalactam, is described. The key step of the sequence involves addition and elimination of an enolic lactam in a single step and 70% yield, employing an organocuprate reagent. The resulting alpha,beta-unsaturated lactam could be condensed with isobutyraldehyde to produce Z-pulchellalactam or converted into siloxypyrrole, which was subjected to the BF(3) x Et(2)O-promoted coupling reaction with isobutyraldehyde to afford E-pulchellalactam after E1-cB elimination and TFA deprotection. This first total synthesis afforded Z-pulchellalactam in six steps and 32% overall yield from Boc-glycine. The same sequence of reactions could also be applied to the liquid- or solid-phase synthesis of trifunctionalized pulchellalactam derivatives.