A structural basis for different antifreeze protein roles

Antifreeze proteins (AFPs) are produced by a variety of organisms to either protect them from freezing or help them tolerate being frozen. Recent structural work has shown that AFPs bind to ice using ordered surface waters on a particular surface of the protein called the ice-binding site (IBS). These 'anchored clathrate' waters fuse to particular planes of an ice crystal and hence irreversibly bind the AFP to its ligand. An AFP isolated from the perennial ryegrass, Lolium perenne (LpAFP) was previously modelled as a right-handed beta helix with two proposed IBSs. Steric mutagenesis, where small side chains were replaced with larger ones, determined that only one of the putative IBSs was responsible for binding ice. The mutagenesis work also partly validated the fold of the computer-generated model of this AFP. In order to determine the structure of the protein, LpAFP was crystallized and solved to 1.4 Å resolution. The protein folds as an untwisted left-handed beta-helix, of opposite handedness to the model. The IBS identified by mutagenesis is remarkably flat, but less regular than the IBS of most other AFPs. Furthermore, several of the residues constituting the IBS are in multiple conformations. This irregularity may explain why LpAFP causes less thermal hysteresis than many other AFPs. Its imperfect IBS is also argued to be responsible for LpAFP's heightened ice-recrystallization inhibition activity. The structure of LpAFP is the first for a plant AFP and for a protein responsible for providing freeze tolerance rather than freeze resistance. To help understand what constitutes an IBS, a non-ice-binding homologue of type III AFP, sialic acid synthase (SAS), was engineered for ice binding. Point mutations were made to the germinal IBS of SAS to mimic key features seen in type III AFP. The crystal structures of some of the mutant proteins showed that the potential IBS became less charged and flatter as the mutations progressed, and ice affinity was gained. This proof-of-principle study highlights some of the difficulties in AFP engineering.

Co-melt fluidised bed granulation of pharmaceutical powders: Improvements in drug bioavailability

This study investigates the use of co-melt fluidised bed granulation for the agglomeration of model pharmaceutical powders, namely, lactose mono-hydrate, PEG 10000, poly-vinyl pyrolidone and ibuprofen as a model drug. Granulation within the co-melt system was found to follow a nucleationâ??steady growthâ??coating regime profile. Using high molecular weight PEG binder, the granulation mechanism and thus the extent of granulation was found to be significantly influenced by binder viscosity. The compression properties of the granulate within the hot fluidised bed were correlated using a novel high temperature experimental procedure. It was found that the fracture stress and fractural modulus of the materials under hot processing conditions were orders of magnitude lower than those measured under ambient conditions. A range of particle velocities within the granulator were considered based on theoretical models. After an initial period of nucleation, the Stokes deformation number analysis indicated that only velocities within the high shear region of the fluidised bed were sufficient to promote significant granule deformation and therefore, coalescence. The data also indicated that larger granules de-fluidised preventing agglomeration by coalescence. Furthermore, experimental data indicated that dissipation of the viscous molten binder to the surface was the most important factor in the latter stages of the granulation process. From a pharmaceutical perspective the inclusion of the model drug, ibuprofen, combined with PVP in the co-melt process proved to be highly significant. It was found that using DSC analysis on the formulations that the decrease in the heat of fusion associated with the melting of ibuprofen within the FHMG systems may be attributed to interaction between PVP and ibuprofen through inter-molecular hydrogen bonding. This interaction decreases the crystallinity of ibuprofen and facilitates solubilisation and bioavailability within the solid matrix.

Chemoenzymatic synthesis of enantiopure dihydroxy-1,2,3,4-tetrahydronaphthalenes from naphthalene and dihydronaphthalene precursors

cis-Dihydrodiol, cis-tetrahydrodiol and arene hydrate bacterial metabolites, of naphthalene and 1,2-dihydronaphthalene, have been used as synthetic precursors; chemoenzymatic and enzyme-catalysed syntheses have been used to obtain all possible enantiopure samples of dihydroxy-1,2,3,4-tetrahydronaphthalene stereoisomers.

Utilization of analgesics, sedatives, and pain scores in infants with a prolonged hospitlaization: A prospective descriptive cohort study

Aim
Describe the utilization of analgesic and sedative medications and documentation of pain scores in a cohort of critically ill infants in a neonatal intensive care unit.

Method
A prospective, longitudinal, cohort study of infants with a predicted length of stay =28 days. Dosages and routes of administration of analgesic and sedative medications and documentation of pain scores were collected on a daily basis.

Results
55 infants were enrolled into the study. Oral sucrose was administered to all 55 infants, 51 infants (93%) were administered enteral acetaminophen and 50 (91%) infants were administered morphine during their hospitalization. Sedatives were administered to 42 infants (76%); 36 (65%) were administered chloral hydrate and 32 (58%) were administered intravenous midazolam. With the exception of the first week of admission, when there was highest utilization of opioids and lower use of sucrose, acetaminophen and sedatives, the pattern of administration of analgesic and sedative agents remained relatively constant throughout the hospitalization. Pain scores were documented for 36 (65%) infants during their hospitalisation, however for these 36 infants, pain scores were infrequently recorded.

Conclusion
There was substantial and varied analgesic and sedative use in this cohort of infants, yet infrequent documentation of pain assessment scores. These practices highlight important clinical implications for sick infants requiring careful consideration of pain and distress management.

Ionic liquids are not always green: hydrolysis of 1-butyl-3-methylimidazolium hexafluorophosphate

1-Butyl-3-methylimidazolium fluoride hydrate has been identified crystallographically as a decomposition product created during purification of the hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate. This highlights the need to treat ionic liquids much as one would any other research chemical with potentially hazardous properties, unknown toxicity and/or stability, particularly when searching for 'green solvents'.

Facile in situ synthesis of nanofluids based on ionic liquids and copper oxide clusters and nanoparticles

Two stable nanofluids comprising of mixed valent copper(_I,_II) oxide clusters (<1 nm) suspended in 1-butyl-3-methylimidazolium acetate, [C(₄)mim][OAc], and copper(_II) oxide nanoparticles (<50 nm) suspended in trioctyl(dodecyl) phosphonium acetate, [P-₈₈₈₁₂][OAc], were synthesised in a facile one-pot reaction from solutions of copper(_II) acetate hydrate in the corresponding ionic liquids. Formation of the nanostructures was studied using ¹³C NMR spectroscopy and differential scanning calorimetry (DSC). From a solution of Cu(OAc)₂ in 1-ethyl-3-methylimidazolium acetate, [C₂mim][OAc], crystals were obtained that revealed the structure of [C₂mim][Cu₃(OAc)₅(OH)₂(H₂O)]center dot H₂O, indicating the formation of copper hydroxo-clusters in the course of the reaction. Synthesised nanostructures were studied using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Physical properties of the prepared IL-nanofluids were examined using IR and UV-VIS spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and densitometry. 

THE EFFECT OF POWER ULTRASOUND ON THE OXIDATIVE DISSOLUTION OF RUO2.XH2O BY BROMATE IONS

The effects of continuous sonication and presonication on the kinetics of oxidative dissolution of ruthenium dioxide hydrate by bromate ions under acidic conditions are reported. Compared with unsonicated and presonicated dispersions the overall rate of dissolution of continuously sonicated dispersions is significantly greater due to a reduction in the average particle size and, hence, an increase in the specific surface area. Powder dispersions subjected to continuous ultrasound and presonication exhibit an initial induction period in their corrosion kinetics; the length of this induction period increases with increasing presonication. This corrosion feature is retained in the dissolution kinetics of powder samples which have been subjected to pre-ultrasound, but which are then stirred during the dissolution process. It is believed that this apparent permanent change in the nature of the powder particles is due to the ultrasound induced formation of a very thin layer of a largely unreactive form of ruthenium dioxide (possibly due to partial dehydration) on the surface of the powder particles. A kinetic scheme, based on this model, is used to account for the observed kinetics of dissolution of RuO2 . xH2O which have been subjected to both continuous sonication and presonication.

Isomorphism between ice and silica

Both ice and silica crystallize into solid-state structures composed of tetrahedral building units that are joined together to form an infinite four-connected net. Mathematical considerations suggest that there is a vast number of such nets and thus potential crystal structures. It is therefore perhaps surprising to discover that, despite the differences in the nature of interatomic interactions in these materials, a fair number of commonly observed ice and silica phases are based on common nets. Here we use computer simulation to investigate the origin of this symmetry between the structures formed for ice and silica and to attempt to understand why it is not complete. We start from a comparison of the dense phases and then move to the relationship between the different open (zeolitic and clathratic) structures formed for both materials. We show that there is a remarkably strong correlation between the energetics of isomorphic silica and water ice structures and that this correlation arises because of the strong link between the total energy of a material and its local geometric features. Finally, we discuss a number of as yet unsynthesized low-energy structures which include a phase of ice based on quartz, a silica based on the structure of ice VI, and an ice clathrate that is isomorphic to the silicate structure nonasil.

Chemoenzymatic synthesis of monocyclic arene oxides and arene hydrates from substituted benzene substrates

Enantiopure cis-dihydrodiol bacterial metabolites of substituted benzene substrates were used as precursors, in a chemoenzymatic synthesis of the corresponding benzene oxides and of a substituted oxepine, via dihydrobenzene oxide intermediates. A rapid total racemization of the substituted benzene 2,3-oxides was found to have occurred, via their oxepine valence tautomers, in accord with predictions and theoretical calculations. Reduction of a substituted arene oxide to yield a racemic arene hydrate was observed. Arene hydrates have also been synthesised, in enantiopure form, from the corresponding dihydroarene oxide or trans-bromoacetate precursors. Biotransformation of one arene hydrate enantiomer resulted in a toluene-dioxygenase catalysed cis-dihydroxylation to yield a benzene cis-triol metabolite.

Factors influencing the compressive strengths of fly ash based geopolymers

Several factors affecting the reactivity of pulverised fuel ash (pfa) as a precursor for geopolymer concrete have been investigated. These include physical and chemical properties of various pfa sources, inclusion of ground granulated blast furnace slag (ggbs), chemical activator dosages and curing temperature. Alkali-activated pfa was found to require elevated curing temperatures and high alkali concentrations. A mixture of sodium hydroxide and sodium silicate was used and this was shown to result in high strengths, as high as 70 MPa at 28-days. The presence of silicates in solution was found to be a key factor. Detailed physical and chemical characterisation was carried out on thirteen pfa sources from the UK. The most important factor affecting the reactivity was found to be the particle size of pfa. The loss on ignition (LOI) and the amorphous content are also important parameters that need to be considered for the selection of pfa for use in geopolymer concrete. The partial replacement of pfa by ground granulated blast furnace slag (ggbs) was found to be beneficial in not only avoiding the need for elevated curing temperatures but also in improving compressive strengths. Microstructural characterisation with scanning electron microscope (SEM) coupled with energy dispersive X-ray spectroscopy (EDS) was performed on pfa/ggbs pastes. The reaction product of pfa and ggbs in these binary systems was calcium aluminium silicate hydrate gel (C-A-S-H) with inclusion of Na in the structure.

Cement As a Waste Form for Nuclear Fission Products: The Case of 90Sr and Its Daughters

One of the main challenges faced by the nuclear industry is the long-term confinement of nuclear waste. Because it is inexpensive and easy to manufacture, cement is the material of choice to store large volumes of radioactive materials, in particular the low-level medium-lived fission products. It is therefore of utmost importance to assess the chemical and structural stability of cement containing radioactive species. Here, we use ab initio calculations based on density functional theory (DFT) to study the effects of ⁹⁰Sr insertion and decay in C-S-H (calcium-silicate-hydrate) in order to test the ability of cement to trap and hold this radioactive fission product and to investigate the consequences of its β-decay on the cement paste structure. We show that ⁹⁰Sr is stable when it substitutes the Ca²⁺ ions in C-S-H, and so is its daughter nucleus ⁹⁰Y after β-decay. Interestingly, ⁹⁰Zr, daughter of ⁹⁰Y and final product in the decay sequence, is found to be unstable compared to the bulk phase of the element at zero K but stable when compared to the solvated ion in water. Therefore, cement appears as a suitable waste form for ⁹⁰Sr storage.

Novel microporous silicates and mesoporous MCM materials derivatised with inorganic and organometallic complexes

Os materiais microporosos e mesoporosos são potenciais catalisadores heterogéneos. Os zeólitos e outros materiais microporosos do tipo zeolítico tradicionais, têm átomos tetracoordenados no esqueleto. Nos últimos anos, um vasto número de titanossilicatos contendo Ti(IV) hexacoordenado e Si(IV) tetracoordenado, com estruturas tridimensionais, têm sido alvo de grande interesse. Um dos objectivos desta tese foi preparar silicatos microporosos, contendo átomos metálicos com número de coordenação superior a quatro, e possuindo quer novas estruturas quer propriedades físicas e químicas interessantes. Neste contexto, foi preparado um novo ítriossilicato de sódio, AV-1, análogo do raro mineral montregianite, Na4K2Y2Si16O38·10H2O. Este material é o primeiro sólido microporoso que contem quantidades estequiométricas de sódio (e ítrio) no esqueleto. Foi, também, sintetizado um silicato de cério, AV-5, análogo estrutural do mineral montregianite com potencial aplicação em optoelectrónica. Nesta tese é, ainda, descrita a síntese e caracterização estrutural de um silicato de cálcio hidratado, AV-2, análogo do raro mineral rhodesite (K2Ca4Na2Si16O38.12H2O). Na continuação do trabalho desenvolvido em Aveiro na síntese de novos titanossilicatos surgiu o interesse de preparar novos zirconossilicatos microporosos por síntese hidrotérmica. Foram preparados dois novos materiais análogos dos minerais petarasite Na5Zr2Si3O18(Cl,OH)·2H2O (AV-3) e kostylevite, K2Si3O9·H2O (AV-8). Foram, também, obtidos análogos sintéticos dos minerais parakeldyshite e wadeite, por calcinação a alta temperatura de AV-3 e de umbite sintética. A heterogeneização de complexos organometálicos na superfície de materiais mesoporosos do tipo M41S permite associar a grande actividade catalítica e a presença de sítios activos localizados típicos dos complexos organometálicos, com a robustez e fácil separação, características dos materiais mesoporosos siliciosos. Nesta dissertação relata-se a derivatização dos materiais MCM-41 e MCM-48 através da reacção de [SiMe2{(h5-C5H4)2}]Fe e [SiMe2{(h5-C5H4)2}]TiCl2 com os grupos silanol das superfícies mesoporosas. Os materiais MCMs derivatizados com ansa-titanoceno foram testados na epoxidação de cicloocteno a 323 K na presença de hidrogenoperóxido de t-butilo. Estudou-se a heterogeneização dos sais de complexos com ligação metal-metal [Mo2(MeCN)10][BF4]4, [Mo2(m-O2CMe)2(MeCN)6][BF4]2 e [Mo2(m- O2CMe)2(dppa)2(MeCN)2][BF4]2 via imobilização nos canais do MCM-41. A imobilização dos catalisadores homogéneos na superfície do MCM-41 envolve a saída dos ligandos nitrilo lábeis, preferencialmente em posição axial, através da reacção com os grupos Si-OH da sílica. Verificou-se que a ligação Mo-Mo se mantém intacta nos produtos finais. É provável que estes materiais sejam eficientes catalisadores heterogéneos em reacções de polimerização. As técnicas de caracterização utilizadas nesta tese foram a difracção de raios-X de pós, a microscopia electrónica de varrimento, a espectroscopia de ressonância magnética nuclear do estado sólido (núcleos 13C, 23Na e 29Si), as espectroscopias de Raman e infravermelho com transformadas de Fourier, as análises termogravimétricas e as análises de adsorção de água e azoto.

Síntese e transformações de compostos do tipo pirazol e 1,2,3-triazol

Compostos do tipo pirazol e 1,2,3-triazol encontram-se presentes em inúmeras moléculas biologicamente ativas. Muitos fármacos atualmente comercializados ou em fase de estudos clínicos contêm na sua estrutura base núcleos de pirazol ou 1,2,3-triazol. Por isso, estes compostos têm sido alvo de intensa pesquisa na procura de novas moléculas com potenciais aplicações medicinais e agroquímicas. Nesta dissertação são descritas novas vias de síntese de novos compostos do tipo pirazol e 1,2,3-triazol. No primeiro capítulo apresenta-se uma breve revisão bibliográfica sobre a atividade biológica, ocorrência natural e métodos de síntese de pirazóis e seus derivados. O segundo capítulo foca-se na síntese de (E)-2-estiril-3-halo-4H-cromen-4-onas e sua transformação em 3(5)-aril-5(3)-[2-(2-hidroxifenil)-2-oxoetil-1H-pirazóis. Em primeiro lugar faz-se uma revisão bibliográfica sobre as (E)-2-estiril-4H-cromen-4-onas e a sua semelhança estrutural com as flavonas, a sua importância e ocorrência natural e métodos de síntese. São ainda abordadas as metodologias mais utilizadas para a síntese de derivados halogenados de (E)-2-estiril-4H-cromen-4-onas. Seguidamente são apresentados e discutidos os resultados da síntese de (E)-3-bromo-2-estiril-4H-cromen-4-onas através da reação de 5-aril-3-hidroxi-1-(2-hidroxifenil)penta-2,4-dien-1-onas com NBS, sob irradiação com micro-ondas, tendo sido estabelecida uma nova metodologia mais eficiente, rápida e regiosseletiva para a síntese de (E)-3-bromo-2-estiril-4H-cromen-4-onas, na ausência de solvente. São igualmente apresentados os resultados da síntese regiosseletiva de (E)-2-estiril-3-iodo-4H-cromen-4-onas através da reação de 5-aril-3-hidroxi-1-(2-hidroxifenil)penta-2,4-dien-1-onas com NIS e TFA/TFAA/NaOAc. Em ambos os métodos de halogenação desenvolvidos, obtiveram-se como produtos secundários as (E)-2-estiril-4H-cromen-4-onas correspondentes. Seguidamente é apresentado o estudo da reação de (E)-2-estiril-3-halo-4H-cromen-4-onas com hidrato de hidrazina. Ao contrário do esperado, obtiveram-se os 3(5)-aril-5(3)-[2-(2-hidroxifenil)-2-oxoetil-1H-pirazóis através de uma reação de adição conjugada 1,6-, de hidrazina à posição C- da cromona com consequente abertura do anel, seguida de uma adição conjugada 1,4- intramolecular. Estes resultados demonstraram que esta reação segue um mecanismo diferente daquele que está reportado na literatura para a reação de (E)-2-estiril-4H-cromen-4-onas não halogenadas em C-3 com hidrato de hidrazina. No terceiro capítulo apresenta-se uma breve revisão bibliográfica sobre as propriedades, aplicações e metodologias de síntese de 1,2,3-triazóis, dando mais relevância às reações de cicloadição 1,3-dipolar e de “click-chemistry”. Seguidamente descrevem-se os resultados obtidos na reação de (E)-5(3)-estiril-3(5)-(2-hidroxifenil)-1H-pirazóis com a azida de sódio para obtenção de díades pirazol-1,2,3-triazol. No entanto esta reação deu origem a novos 5(3)-(2-aril-2-azidoetil)-3(5)-(2-hidroxifenil)-1H-pirazóis e não às díades pirazol-1,2,3-triazol pretendidas. Como o resultado não foi o esperado, desenvolveu-se outra metodologia de síntese, que envolve, num primeiro, a reação de (E)-2-estiril-4H-cromen-4-onas com azida de sódio, dando origem a 5(4)-aril-4(5)-(cromon-2-il)-1H-1,2,3-triazóis. No passo seguinte, efetuou-se a reação destes compostos com hidrato de hidrazina tendo ocorrido a formação das diades 5(4)-aril-4(5)-[3(5)-(2-hidroxifenil)-1H-pirazol-5(3)-il]-1H-1,2,3-triazol pretendidas. No quarto capítulo, estudou-se a reatividade de (E)-5(3)-estiril-3(5)-(2-hidroxifenil)-1H-pirazóis em reações de iodação com vista à obtenção de 4-iodo-1H-pirazóis. Apresenta-se uma breve revisão bibliográfica sobre os diferentes métodos descritos na literatura para a iodação de compostos heterocíclicos aromáticos, nomeadamente para a obtenção de 4-iodo-1H-pirazóis. Dos vários sistemas de iodação testados, o sistema oxidativo I2/CAN foi o que deu melhores resultados na iodação dos (E)-5(3)-estiril-3(5)-(2-hidroxifenil)-1H-pirazóis. Este método permitiu iodar a posição C-4 do núcleo de pirazol apenas para os derivados que possuem o grupo nitro ou o átomo de cloro no anel do grupo estirilo, obtendo-se o 3(5)-(2-hidroxifenil)-4-iodo-5(3)-(4-nitrofenil)vinil-1H-pirazol e o 5(3)-(4-clorofenil)vinil)-3(5)-(2-hidroxi-5-iodofenil)-4-iodo-1H-pirazol; no entanto, para os restantes derivados, verificou-se apenas a iodação nas posições ativadas do anel fenólico. Todos os novos compostos sintetizados foram caraterizados estruturalmente recorrendo a estudos de espetroscopia de ressonância magnética nuclear (RMN) mono e bidimensionais. Sempre que possível, para uma caraterização estrutural mais completa, foram efetuados espetros de massa (EM) e análises elementares ou espetros de massa de alta resolução (EMAR) para todos os novos compostos sintetizados. Finalmente são apresentadas as conclusões gerais deste trabalho e perspetivas futuras.

Electrospun Contrast Agent-Loaded Fibers for Colon-Targeted MRI

Magnetic resonance imaging is a diagnostic tool used for detecting abnormal organs and tissues, often using Gd(III) complexes as contrast-enhancing agents. In this work, core–shell polymer fibers have been prepared using coaxial electrospinning, with the intent of delivering gadolinium (III) diethylenetriaminepentaacetate hydrate (Gd(DTPA)) selectively to the colon. The fibers comprise a poly(ethylene oxide) (PEO) core loaded with Gd(DTPA), and a Eudragit S100 shell. They are homogeneous, with distinct core–shell phases. The components in the fibers are dispersed in an amorphous fashion. The proton relaxivities of Gd(DTPA) are preserved after electrospinning. To permit easy visualization of the release of the active ingredient from the fibers, analogous materials are prepared loaded with the dye rhodamine B. Very little release is seen in a pH 1.0 buffer, while sustained release is seen at pH 7.4. The fibers thus have the potential to selectively deliver Gd(DTPA) to the colon. Mucoadhesion studies reveal there are strong adhesive forces between porcine colon mucosa and PEO from the core, and the dye-loaded fibers can be successfully used to image the porcine colon wall. The electrospun core–shell fibers prepared in this work can thus be developed as advanced functional materials for effective imaging of colonic abnormalities.

Heats of formation of some hydrates /|nA. Phillipson. -- 260 St. Catharines, Ont. : [s. n.],

A great deal of data on the heats of formation of various hydrates has been compiled i n the J.A.N.A.F. and other tables such as the National Bureau of Standards circulars. Comparison of the heat of f ormation of a hydrate with that of the corresponding anhydrate exposes anomalies i n a surprising number of cases. Some of the results are so discordant that i t is apparent that one or the other value is seriously mistaken. No attempt has been made i n this work to determine which value may be correct, but measurements have been made of the difference between these two values. The procedure adopted has been to dissolve the hydrate and the anhydrate, to achieve the same final concentration of the compound in solution, and so to measure the difference in heats of solution .. Measurements were made at OOC in a modified Bunsen ice calorimeter, well insulated and surrounded by an icewater mixture . The observed differences in heats of solut ion were corrected t o 25°0 by using appropriate heat capacity data. These differences offer a direct measure of the enthalpy involved in binding a mole of water into the crystal structure and so should shed light on the nature of binding involved. The following hydrates were studied : MgS04.nH20 (n = 1,4,7), MnC12.nH20 (n = 1, 2), LiI. nH20 (n = 1,3), MnS04. nH20 (n = 1,4), CaC12. nH20 (n = 2,6) , K2C03.1~H20, LiCl.H20, LiBr.2H20, CdC12.2t H2o, and N2H4eH20.