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PubMed1998

In-house development of test equipment for quality control and training. Case study: a prototype ECG simulator-tester.

The support services for biomedical technology address a variety of technical and administrative issues, concerning the safe and efficient operation of medical equipment over the period of its intended use and the training of hospital personnel in issues concerning safety and quality. Clinical Engineering Departments undertake the responsibility of developing and operating training programs in medical equipment utilisation apart from the traditional role of training and supervising technicians involved in testing, calibration and preventive/corrective maintenance of electromedical equipment. In view of the above, the Institute of Biomedical Technology and the Centre of Biomedical Engineering collaborated for the design and development of a prototype digital ECG and arrhythmia simulator. In the absence of internationally accepted inspection protocols for ECG simulators, the verification phase of the project involved mainly the inspection of the device's conformity to its initial technical specifications. The results demonstrated that this tester. due to simplicity in construction and easiness of use could be a practical, reliable and economical solution for electrocardiograph and ECG monitor testing and waveform recognition training.

Arrhythmias, Cardiac↗
PubMed2002

Requirements and prototyping of a home health care application based on emerging JAVA technology.

IT support for home health care is an expanding area within health care IT development. Home health care differs from other in- or outpatient care delivery forms in a number of ways, and thus, the introduction of home health care applications must be based on a rigorous analysis of necessary requirements to secure safe and reliable health care. This article reports early experiences from the development of a home health care application based on emerging JAVA technologies. A prototype application for the follow-up of diabetes patients is presented and discussed in relation to a list of general requirements on home health care applications.

Blood Glucose Self-Monitoring↗
PubMed2003

Bacterial serine palmitoyltransferase: a water-soluble homodimeric prototype of the eukaryotic enzyme.

Serine palmitoyltransferase (SPT, EC 2.3.1.50) is a key enzyme in sphingolipid biosynthesis and catalyzes the decarboxylative condensation of L-serine and palmitoyl coenzyme A (CoA) to 3-ketodihydrosphingosine (KDS). We found that the gram-negative obligatory aerobic bacteria Sphingomonas paucimobilis EY2395(T) have significant SPT activity, and purified SPT to homogeneity. Unlike eukaryotic enzymes, this enzyme was a water-soluble homodimeric protein. We isolated the SPT gene encoding 420 amino acid residues (M(r) 45,041) and succeeded in overproducing the SPT protein in Escherichia coli, in which the product amounted to about 10-20% of the total protein of the cell extract. Sphingomonas SPT showed about 30% homology with the enzymes of the alpha-oxamine synthase family, and amino acid residues supposed to be involved in catalysis are conserved. The purified recombinant-SPT showed the characteristic absorption spectrum derived from its coenzyme pyridoxal 5'-phosphate (PLP). The addition of the substrate, L-serine, caused spectral changes indicating the formation of the external aldimine intermediate. Sphingomonas SPT is a prototype of the eukaryotic enzyme and would be a useful model to elucidate the reaction mechanism of SPT.

Acyltransferases↗
PubMed1979

Haemagglutination-inhibiting (HI) antibodies against four prototype strains of influenza A virus in different age groups.

Sera of 197 apparently well persons were tested for residual haemagglutination-inhibiting antibodies against live Hong Kong/68, A/FM/47 and A/PR/34 strains. Sera of 62 well persons, regularly exposed to contacts with swine, were tested against an inactivated A/New Jersey/76 antigen. Those born some time before and during a certain influenza era showed a significantly greater proportion of homologous residual titres against the subtype prevailing in that influenza era, than those born after the termination of the same era. In each of the seven age groups tested both the percentage of positives and the geometric mean titres were usually highest against the Hong Kong strain (representing the most recent era); the next highest were those against the FM1 strain and the lowest were those against the PR8 strain (representing the most distant of these three influenza eras). The serological involvement of donors exposed to regular contacts with swine was relatively stronger against the New Jersey antigen than the response of other serum donors shown against the other three, more recent, prototypes of influenza virus A. The oldest age groups showed significantly lower antibody response against the PR8, FM1 and Hong Kong strains (but not against the New Jersey antigen) than the next one or two of the younger age groups.

Adolescent↗
PubMed1973

Antigenic analysis of prototype influenza A (H3N2) strains by the antiserum absorption method.

Prototype strains of the influenza A (H3N2) virus can be arranged on a gradient showing the degree of the antigenic drift which the haemagglutinins of the strains have undergone. The demonstration of fine antigenic differences is based on an antiserum absorption test which allows a detailed antigenic analysis of strains. The gradient provides information on variation in strains occurring in different geographical areas and its use may be helpful in differentiating between introduced strains and locally developing variants.

Absorption↗
PubMed2003

Rapid prototyping of 2D structures with feature sizes larger than 8 microm.

This paper extends rapid prototyping for several types of lithography to the 8-25-microm size range, using transparency photomasks prepared by photoplotting. It discusses the technical improvement in photomask quality achieved by photoplotting, compared to the currently used image setting, and demonstrates differences in the resolution that can be obtained with photomasks with features in the 8-100-microm size range. These high-resolution photomasks were used to microfabricate microelectrodes, microlenses, and stamps for microcontact printing, following methods described previously.

Biological Assay↗
PubMed2000

Fabrication of topologically complex three-dimensional microfluidic systems in PDMS by rapid prototyping.

This paper describes a procedure for making topologically complex three-dimensional microfluidic channel systems in poly(dimethylsiloxane) (PDMS). This procedure is called the "membrane sandwich" method to suggest the structure of the final system: a thin membrane having channel structures molded on each face (and with connections between the faces) sandwiched between two thicker, flat slabs that provide structural support. Two "masters" are fabricated by rapid prototyping using two-level photolithography and replica molding. They are aligned face to face, under pressure, with PDMS prepolymer between them. The PDMS is cured thermally. The masters have complementary alignment tracks, so registration is straightforward. The resulting, thin PDMS membrane can be transferred and sealed to another membrane or slab of PDMS by a sequence of steps in which the two masters are removed one at a time; these steps take place without distortion of the features. This method can fabricate a membrane containing a channel that crosses over and under itself, but does not intersect itself and, therefore, can be fabricated in the form of any knot. It follows that this method can generate topologically complex microfluidic systems; this capability is demonstrated by the fabrication of a "basketweave" structure. By filling the channels and removing the membrane, complex microstructures can be made. Stacking and sealing more than one membrane allows even more complicated geometries than are possible in one membrane. A square coiled channel that surrounds, but does not connect to, a straight channel illustrates this type of complexity.

Dimethylpolysiloxanes↗
PubMedDate not supplied

Polycefin, a new prototype of a multifunctional nanoconjugate based on poly(beta-L-malic acid) for drug delivery.

A new prototype of nanoconjugate, Polycefin, was synthesized for targeted delivery of antisense oligonucleotides and monoclonal antibodies to brain tumors. The macromolecular carrier contains: 1. biodegradable, nonimmunogenic, nontoxic beta-poly(L-malic acid) of microbial origin; 2. Morpholino antisense oligonucleotides targeting laminin alpha4 and beta1 chains of laminin-8, which is specifically overexpressed in glial brain tumors; 3. monoclonal anti-transferrin receptor antibody for specific tissue targeting; 4. oligonucleotide releasing disulfide units; 5. L-valine containing, pH-sensitive membrane disrupting unit(s), 6. protective poly(ethylene glycol); 7. a fluorescent dye (optional). Highly purified modules were conjugated directly with N-hydroxysuccinimidyl ester-activated beta-poly(L-malic acid) at pendant carboxyl groups or at thiol containing spacers via thioether and disulfide bonds. Products were chemically validated by physical, chemical, and functional tests. In vitro experiments using two human glioma cell lines U87MG and T98G demonstrated that Polycefin was delivered into the tumor cells by a receptor-mediated endocytosis mechanism and was able to inhibit the synthesis of laminin-8 alpha4 and beta1 chains at the same time. Inhibition of laminin-8 expression was in agreement with the designed endosomal membrane disruption and drug releasing activity. In vivo imaging showed the accumulation of intravenously injected Polycefin in brain tumor tissue via the antibody-targeted transferrin receptor-mediated endosomal pathway in addition to a less efficient mechanism known for high molecular mass biopolymers as enhanced permeability and retention effect. Polycefin was nontoxic to normal and tumor astrocytes in a wide range of concentrations, accumulated in brain tumor, and could be used for specific targeting of several biomarkers simultaneously.

Animals↗
PubMed1995

Gramicidin S synthetase 1 (phenylalanine racemase), a prototype of amino acid racemases containing the cofactor 4'-phosphopantetheine.

The biosynthesis of the decapeptide antibiotic gramicidin S in Bacillus brevis ATCC 9999 is catalyzed by a multienzyme system consisting of two multifunctional proteins, gramicidin S synthetase 1 and 2, encoded by the grsA and grsB genes, respectively. Gramicidin S synthetase 1 (phenylalanine racemase, EC 5.1.1.11, GS1) racemizes phenylalanine in the thioester-bound stage. The amount of 4'-phosphopantetheine liberated from highly purified GS1 was determined microbiologically using Lacto-bacillus plantarum as the test organism. It matches exactly with the amount of L-[14C]phenylalanine covalently incorporated by GS1 as thioester. The reaction center of GS1 for L-phenylalanine thiolation and racemization was labeled with [3H]iodoacetic acid. After tryptic fragmentation of the 3H-carboxymethylated enzyme, the active site peptide for thioester binding and racemization of phenylalanine was isolated in pure form by multistep methodology and investigated by sequence, amino acid, and mass spectrometric analysis. A 4'-phosphopantetheine carrier was found to be attached to the active site serine of the consensus motif LGGDSI forming the thiolation site of phenylalanine. These specific properties establish GS1 as a prototype of amino acid racemases using 4'-phosphopantetheine as a cofactor and yield further evidence that multiple Pan carriers are involved in gramicidin S formation. Our results are strong evidence for the "multiple carrier model" as a new concept of nonribosomal peptide biosynthesis at protein templates as recently proposed [Stein, T., et al. (1994) FEBS Lett. 340, 39-44].

Amino Acid Isomerases↗
PubMed1992

Experimental and computational infrared CD studies of prototypical peptide conformations.

The infrared vibrational circular dichroism (VCD) spectral features of prototypical peptide secondary structures were reported previously by Yasui and Keiderling [Yasui, S.C., & Keiderling, T.A. (1986) Biopolymers 25, 5]. These results demonstrated that the "random coil" peptide conformation exhibits VCD signals which are approximately mirror-image features of those exhibited by alpha-helical conformers. We report here a comparison of observed VCD spectra with those computed for several secondary structures, using the extended coupled oscillator formalism employed previously to compute VCD spectra of model DNA [Zhong et al. (1990) Biochemistry 29, 7485]. These studies suggest that the so-called random-coil peptide conformation has distinct short-range order and appears to be a left-handed, helical structure.

Circular Dichroism↗
PubMed1988

Structural and dynamic aspects of binding of a prototype lexitropsin to the decadeoxyribonucleotide d(CGCAATTGCG)2 deduced from high-resolution 1H NMR Studies.

Structural and dynamic properties of the self-complementary decadeoxyribonucleotide d(CGCAATTGCG)2 and the interaction between a prototype lexitropsin, or information-reading oligopeptide, and the decadeoxyribonucleotide are deduced by using high-resolution 1H NMR techniques. The nonexchangeable and imino proton resonances of d(CGCAATTGCG)2 have been completely assigned by two-dimensional NMR studies. The decadeoxyribonucleotide exists as a right-handed B-DNA. In the 1H NMR spectrum of the 1:1 complex, the selective chemical shifts and removal of degeneracy of AH2(4), AH2(5), T-CH3(6), and T-CH3(7) due to the anisotropy effects of the heterocyclic moieties of the ligand, and with lesser effects at the flanking base sites C(3) and G(8), locate the drug centrally in the decadeoxyribonucleotide. This conclusion is supported by plots of individual chemical shift changes across the decadeoxyribonucleotide. Similarly, imino protons IV and V experience larger shifts and II and III smaller shifts in accord with this conclusion while drug complexation permits the detection of imino proton I. Strong nuclear Overhauser effects (NOEs) between pyrrole H5 and AH2(5), and weaker NOEs to AH1'(5), TH3'(6), and AH2'(5), firmly locate the ligand in the minor groove. Intraligand NOEs between the adjacent heterocyclic moieties indicate that the lexitropsin is subject to propeller twisting about the N6-C9 bond in both the bound and free forms. Nuclear Overhauser effect spectroscopy (NOESY) and correlated spectroscopy (COSY) experiments also indicate that the removal of degeneracy of the C16 methylene protons upon complexation may arise from restricted rotation about the C15-N9, C15-C16, and C16-C17 bonds. Specific hydrogen bonds between amide NH groups on the concave face of the ligand (N4H, N6H, N9H) and adenine N3 or thymine O2 on the floor of the minor groove are in accord with displacement of the hydration shell by the drug. NOE measurements on the decadeoxyribonucleotide in the 1:1 complex confirm it exists as a right-handed helix and belongs to the B family. Exchange NMR effects permit an estimate of a rate of approximately equal to 44 s-1 for the two-site exchange of the lexitropsin between two equivalent sites on the decamer with delta G++ approximately equal to 70 +/- 5 kJ mol-1 at 294 K. Alternative mechanisms for this exchange process are considered.

Base Sequence↗
PubMed2005

Identification and visualization of the dimerization initiation site of the prototype lentivirus, maedi visna virus: a potential GACG tetraloop displays structural homology with the alpha- and gamma-retroviruses.

Dimerization of retroviral genomic RNA is essential for efficient viral replication and is mediated by structural interactions between identical RNA motifs in the viral leader region. We have visualized, by electron microscopy, RNA dimers formed from the leader region of the prototype lentivirus, maedi visna virus. Characterization by in vitro assays of the domains responsible for this interaction has identified a 20 nucleotide sequence that functions as the core dimerization initiation site. This region is predicted to form a GACG tetraloop and therefore differs significantly from the kissing loop palindromes utilized to initiate dimerization in primate lentiviruses. The motif is strongly conserved across the ovine and caprine lentiviruses, implying a critical functional role. Furthermore, the proposed GACG tetraloop exhibits marked structural homology with similar structural motifs present in the leader regions of the alpha- and gamma-retroviruses, and the maedi visna virus dimer linkage region is capable of forming heterodimeric species with the Moloney murine leukemia virus Psi domain. This may be indicative of commonality of origin of the two viruses or convergent evolution.

Animals↗
PubMed2006

Proposal for a hydrogen bond network in the active site of the prototypic gamma-class carbonic anhydrase.

The crystal structure of Cam, the prototypic gamma-class carbonic anhydrase, reveals active site residues Gln75, Asn73, and Asn 202 previously hypothesized to participate in catalysis. These potential roles were investigated for the first time by kinetic analyses of site-specific replacement variants of the zinc and cobalt forms of Cam. Gln75 replacement variants showed large decreases in k(cat)/K(m) relative to wild-type. Further, the Gln75 variants showed a loss of the pK(a) in pH versus k(cat)/K(m) profiles previously attributed to ionization of the metal-bound water yielding the hydroxyl group attacking CO(2). These results support the previously proposed role for Gln75 in hydrogen bonding with the catalytic hydroxyl orienting it for attack on CO(2). Kinetic analyses of Asn73 variants were consistent with a role in hydrogen bonding with Gln75 to position it for optimal interaction with the catalytic hydroxyl. Kinetic analyses of Asn202 variants showed substantial decreases in k(cat)/K(m) relative to the wild-type enzyme supporting the previously hypothesized role in polarizing CO(2) and facilitating attack from the metal-bound hydroxyl. On the basis of results presented here, and previously reported structural analyses, we present a catalytic mechanism involving Gln75, Asn73, and Asn202 that also suggests a role for Glu62 not previously recognized. Finally, the results suggest that the gamma-, beta-, and alpha-class carbonic anhydrases each independently evolved variations of a fundamental hydrogen bond network essential for catalysis.

Asparagine↗
PubMed1997

In vitro biosynthesis of a decasaccharide prototype of multiply branched polylactosaminoglycan backbones.

Multiply branched polylactosaminoglycans are expressed in glycoproteins and glycolipids of many cells. Interest in their biology stems from their abundant expression in early embryonal cells and from their ability to carry multiple lectin-binding determinants, which makes them prominent ligands and antagonists of cell adhesion proteins. A prototype of their backbones is represented by the decasaccharide LacNAc beta1-3'(LacNAc beta1-6')LacNAc beta1-3'(LacNAc beta1-6')LacNAc (5), where LacNAc is the disaccharide Gal beta1-4GlcNAc. Here, we describe in vitro biosynthesis of glycan 5. Incubation of the linear hexasaccharide LacNAc beta1-3'LacNAc beta1-3'LacNAc (1) with UDP-GlcNAc and alpha midchain beta1,6-GlcNAc transferase activity (GlcNAc to Gal), present in rat serum [Gu, J., Nishikawa, A., Fujii, S., Gasa, S., & Taniguchi, N. (1992) J. Biol. Chem. 267, 2994-2999], gave the doubly branched octasaccharide LacNAc beta1-3'(GlcNAc beta1-6')LacNAc beta1-3'(GlcNAc beta1-6')LacNAc (4). The latter was converted to 5 by enzymatic beta1,4-galactosylation. In the initial branching reaction of 1, two isomeric heptasaccharide intermediates, LacNAc beta1-3'LacNAc beta1-3'(GlcNAc beta1-6')LacNAc (2) and LacNAc beta1-3'(GlcNAc beta1-6')LacNAc beta1-3'LacNAc (3), were formed first at comparable rates. Later, both intermediates were converted to 4, revealing two distinct pathways of the reaction: 1 --> 2 --> 4 and 1 --> 3 --> 4. These data suggest that, regardless of their chain length, linear polylactosamines similar to 1 contain potential branching sites at each of the internal galactoses. The enzyme-binding epitope of 1 is probably LacNAc beta1-3'LacNAc, because the trisaccharides GlcNAc beta1-3'LacNAc and LacNAc beta1-3Gal as well as the tetrasaccharide GlcNAc beta1-3'LacNAc beta1-3Gal were poor acceptors, while LacNAc beta1-3'LacNAc was a good one. Midchain beta1,6-GlcNAc transferase activities present in serum of several mammalian species, including man, resembled closely the rat serum activity in their mode of action and in their acceptor specificity. We suggest that analogous membrane-bound Golgi enzymes are involved in the biosynthesis of multiply branched polylactosamines in vivo.

Amino Sugars↗
PubMed2002

Pyrazolyl-bridged iridium dimers. 18.(1) influence of metal-metal bonding on the geometry of diiridium(II) adducts and hydrido-diiridium complexes formed from the diiridium(I) prototype [Ir(mu-pz)(PPh(3))(CO)](2) (pzH = Pyrazole) by dihydrogen addition or protonation.

Slow uptake of molecular dihydrogen by the diiridium(I) prototype [Ir(mu-pz)(PPh(3))(CO)](2) (1: pzH = pyrazole) is accompanied by formation of a 1,2-dihydrido-diiridium(II) adduct [IrH(mu-pz)(PPh(3))(CO)](2) (2), for which an X-ray crystal structure determination reveals that (unlike in 1) the PPh(3) ligands are axial, with the hydrides occupying trans coequatorial positions across the Ir-Ir bond (2.672 A). Reaction with CCl(4) effects hydride replacement in 2, affording the monohydride Ir(2)H(Cl)(mu-pz)(2)(PPh(3))(2)(CO)(2) (3) in which Ir-Ir = 2.683 A. At one metal center, H is equatorial and PPh(3) is axial, while at the other, Cl is axial as is found in the symmetrically substituted product [Ir(mu-pz)(PPh(3))(CO)Cl](2) (4) (Ir-Ir = 2.754 A) that is formed by action of CCl(4) on 1. Treatment of 1 with I(2) yields the diiodo analogue 5 of 4, which reacts with LiAlH(4) to afford the isomorph Ir(2)H(I)(mu-pz)(2)(PPh(3))(2)(CO)(2) (6) of 3 (Ir-Ir = 2.684 A). Protonation (using HBF(4)) of 1 results in formation of the binuclear cation Ir(2)H(mu-pz)(2)(PPh(3))(2)(CO)(2)(+) (7: BF(4)(-) salt), which shows definitive evidence (from NMR) for a terminally bound hydride in solution (CH(2)Cl(2) or THF), but 7 crystallizes as an axially symmetric unit in which Ir-Ir = 2.834 A. Reaction of 7 with water or wet methanol leads to isolation of the cationic diiridium(III) products [Ir(2)H(2)(mu-OX)(mu-pz)(2)(PPh(3))(2)(CO)(2)]BF(4) (8, X = H; 9, X = Me).

Journal Article↗
PubMed1996

Selective Azide Oxidation of 1,2-Bis(diphenylphosphino)benzene and Related Ethylenebis(phosphines) to Asymmetric Multifunctional Phosphorus Ligands and Formation of Rhodium(I) Complexes of These Ligands. Structural Characterization of the Prototypical Ligand 1-(((Trimethylsilyl)imino)diphenylphosphorano)-2-(diphenylphosphino)benzene and Its Rhodium(I) Complex: 1-Ph(2)P=N(SiMe(3))C(6)H(4)-2-(Ph(2)P)Rh(CO)Cl.

Selective azide mono-oxidation of o-bis(phosphines) such as o-bis(diphenylphosphino)benzene and other bis(phosphines) with cis-substituents on a rigid backbone such as an ethylene structure occurs as the result of the steric control exerted during the azide oxidation (Staudinger) reaction process. The azides used were the trimethylsilyl, 4-cyanotetrafluorophenyl, benzyl, and diphenoxyphosphonyl azides. The prototypical ligand 1-Ph(2)P=N(SiMe(3))-2-(Ph(2)P)C(6)H(4), 2, has been structurally characterized. Crystal data for 2: crystal dimensions, 0.38 x 0.38 x 0.57 mm; space group, monoclinic, P2(1)/c, (No. 14); a = 11.093(5) Å, b = 14.898(5) Å, c = 18.811(2) Å, beta = 102.76(2) degrees, V = 3031 Å(3), Z = 4. Final R, R(w) and GOF values were 0.068, 0.074, and 1.92 respectively. The P=N-SiMe(3) angle was wide, 152.7(3) degrees, and the P=N bond length short (1.529(5) Å) relative to arylated iminophosphoranes but in keeping with the trends for silylated analogs. The iminophosphorane center can be selectively transformed with other agents in a Wittig type reaction converting the azides to the monooxide, monosulfide, etc. The iminophosphoranophosphines are also good complexing agents and the Rh(I) complex derived from 2, 1-Ph(2)P=N(SiMe(3))-C(6)H(4)-2-(Ph(2)P)Rh(CO)Cl, 15 was structurally characterized. Crystal data for 15: crystal dimensions, 0.32 x 0.44 x 0.66 mm; space group, monoclinic, P2(1)/c (No. 14); a = 13.793(3) Å, b = 12.622(11) Å, c = 20.436(6) Å, beta = 105.93(2) degrees, V = 3421.2 Å(3), Z = 4. Final R, R(w), and GOF values were 0.064, 0.061, and 1.45 respectively. The complex shows typical square planar geometry about Rh, a cis phosphine-CO relationship, and no exceptional steric crowding of the coordination site.

Journal Article↗
PubMed2003

Prototypal dithiazolodithiazolyl radicals: synthesis, structures, and transport properties.

New synthetic routes to 1,2,3-dithiazolo-1,2,3-dithiazolylium salts, based on double Herz condensations of N-alkylated 2,6-diaminopyridinium salts with sulfur monochloride, have been developed. The two prototypal 1,2,3-dithiazolo-1,2,3-dithiazolyl radicals HBPMe and HBPEt have been prepared and characterized in solution by cyclic voltammetry and EPR spectroscopy. Measured electrochemical cell potentials and computed (B3LYP/6-31G) gas-phase disproportionation enthalpies favor a low on-site Coulombic repulsion energy U in the solid state. The crystal structures of HBPR (R = Me, Et) have been determined by X-ray crystallography (at 293 K). Both consist of slipped pi-stacks of undimerized radicals, with many close intermolecular S- - -S contacts. Magnetic, conductivity, and optical measurements have been performed and the results interpreted in light of extended Hückel band calculations. The crystalline materials are paramagnetic above 100 K, with room-temperature conductivities sigma(RT) of 10(-5)-10(-6) S cm(-1); the slightly greater conductivity of the R = Et compound can be associated with a more well developed band structure. We suggest a Mott-Hubbard insulator ground state for these materials, with an on-site Coulomb repulsion energy U of about 1.0 eV.

Journal Article↗
PubMed2005

Characterization of H2 binding sites in prototypical metal-organic frameworks by inelastic neutron scattering.

The hindered rotor transitions of H(2) adsorbed in the chemically related and prototypical porous metal-organic frameworks IRMOF-1, IRMOF-8, IRMOF-11, and MOF-177 were studied by inelastic neutron scattering to gain information on the specifics of H(2) binding in this class of adsorbents. Remarkably sharp and complex spectra of these materials signify a diversity of well-defined binding sites. Similarities in the spectral features as a function of H(2) loading and correlations with recent crystallographic studies were used to assign transitions ranging in rotational barrier from <0.04 to 0.6 kcal/mol as corresponding to localized adsorption sites on the organic and inorganic components of these frameworks. We find that binding of H(2) at the inorganic cluster sites is affected by the nature of the organic link and is strongest in IRMOF-11 in accord with our adsorption isotherm data. The sites on the organic link have lower binding energies, but a much greater capacity for increases in H(2) loading, which demonstrates their importance for hydrogen uptake by these materials.

Adsorption↗