Prediction of Hydrate and Solvate Formation Using Statistical Models

Novel, knowledge based models for the prediction of hydrate and solvate formation are introduced, which require only the molecular formula as input. A data set of more than 19 000 organic, nonionic, and nonpolymeric molecules was extracted from the Cambridge Structural Database. Molecules that formed solvates were compared with those that did not using molecular descriptors and statistical methods, which allowed the identification of chemical properties that contribute to solvate formation. The study was conducted for five types of solvates: ethanol, methanol, dichloromethane, chloroform, and water solvates. The identified properties were all related to the size and branching of the molecules and to the hydrogen bonding ability of the molecules. The corresponding molecular descriptors were used to fit logistic regression models to predict the probability of any given molecule to form a solvate. The established models were able to predict the behavior of ∼80% of the data correctly using only two descriptors in the predictive model

Starch hydrogels as targeted colonic drug delivery vehicles

Targeted colonic drug delivery systems are needed for the treatment of endemic colorectal pathologies, such as Crohn's disease, ulcerative colitis, and colorectal cancer. These drug delivery vehicles are difficult to formulate, as they need to remain structurally intact whilst navigating a wide range of physiological conditions across the upper gastrointestinal tract. In this work we show how starch hydrogel bulk structural and molecular level parameters influence their properties as drug delivery platforms. The in vitro protocols mimic in vivo conditions, accounting for physiological concentrations of gastrointestinal hydrolytic enzymes and salts. The structural changes starch gels undergo along the entire length of the human gastrointestinal tract have been quantified, and related to the materials' drug release kinetics for three different drug molecules, and interactions with the large intestinal microbiota. It has been demonstrated how one can modify their choice of starch in order to fine tune its corresponding hydrogel's pharmacokinetic profile

Assembly of α-Glucan by GlgE and GlgB in Mycobacteria and Streptomycetes

Actinomycetes, such as mycobacteria and streptomycetes, synthesize α-glucan with α-1,4 linkages and α-1,6 branching to help evade immune responses and to store carbon. α-Glucan is thought to resemble glycogen except for having shorter constituent linear chains. However, the fine structure of α-glucan and how it can be defined by the maltosyl transferase GlgE and branching enzyme GlgB were not known. Using a combination of enzymolysis and mass spectrometry, we compared the properties of α-glucan isolated from actinomycetes with polymer synthesized in vitro by GlgE and GlgB. We now propose the following assembly mechanism. Polymer synthesis starts with GlgE and its donor substrate, α-maltose 1-phosphate, yielding a linear oligomer with a degree of polymerization (∼16) sufficient for GlgB to introduce a branch. Branching involves strictly intrachain transfer to generate a C chain (the only constituent chain to retain its reducing end), which now bears an A chain (a nonreducing end terminal branch that does not itself bear a branch). GlgE preferentially extends A chains allowing GlgB to act iteratively to generate new A chains emanating from B chains (nonterminal branches that themselves bear a branch). Although extension and branching occur primarily with A chains, the other chain types are sometimes extended and branched such that some B chains (and possibly C chains) bear more than one branch. This occurs less frequently in α-glucans than in classical glycogens. The very similar properties of cytosolic and capsular α-glucans from Mycobacterium tuberculosis imply GlgE and GlgB are sufficient to synthesize them both

Self-healing composite coating fabricated with a cystamine crosslinked cellulose nanocrystal stabilized Pickering emulsion

A gelled Pickering emulsion system was fabricated by first stabilizing linseed oil droplets in water with dialdehyde cellulose nanocrystals (DACNCs) and then cross-linking with cystamine. Cross-linking of the DACNCs was shown to occur by a reaction between the amine groups on cystamine and the aldehyde groups on the CNCs, causing gelation of the nanocellulose suspension. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to characterize the cystamine-cross-linked CNCs (cysCNCs), demonstrating their presence. Transmission electron microscopy images evidenced that cross-linking between cysCNCs took place. This cross-linking was utilized in a linseed oil-in-water Pickering emulsion system, creating a novel gelled Pickering emulsion system. The rheological properties of both DACNC suspensions and nanocellulose-stabilized Pickering emulsions were monitored during the cross-linking reaction. Dynamic light scattering and confocal laser scanning microscopy (CLSM) of the Pickering emulsion before gelling imaged CNC-stabilized oil droplets along with isolated CNC rods and CNC clusters, which had not been adsorbed to the oil droplet surfaces. Atomic force microscopy imaging of the air-dried gelled Pickering emulsion also demonstrated the presence of free CNCs alongside the oil droplets and the cross-linked CNC network directly at the oil-water interface on the oil droplet surfaces. Finally, these gelled Pickering emulsions were mixed with poly(vinyl alcohol) solutions and fabricated into self-healing composite coating systems. These self-healing composite coatings were then scratched and viewed under both an optical microscope and a scanning electron microscope before and after self-healing. The linseed oil was demonstrated to leak into the scratches, healing the gap automatically and giving a practical approach for a variety of potential applications

Structural heterogeneities in starch hydrogels

Hydrogels have a complex, heterogeneous structure and organisation, making them promising candidates for advanced structural and cosmetics applications. Starch is an attractive material for producing hydrogels due to its low cost and biocompatibility, but the structural dynamics of polymer chains within starch hydrogels are not well understood, limiting their development and utilisation. We employed a range of NMR methodologies (CPSP/MAS, HR-MAS, HPDEC and WPT-CP) to probe the molecular mobility and water dynamics within starch hydrogels featuring a wide range of physical properties. The insights from these methods were related to bulk rheological, thermal (DSC) and crystalline (PXRD) properties. We have reported for the first time the presence of highly dynamic starch chains, behaving as solvated moieties existing in the liquid component of hydrogel systems. We have correlated the chains’ degree of structural mobility with macroscopic properties of the bulk systems, providing new insights into the structure-function relationships governing hydrogel assemblies

Synthesis and structure of two new high nuclearity Ru/Pt mixed-metal clusters

The reaction of the dianion [Ru5C(CO)14]12- with [PtCl2- (MeCN)2] in the presence of silica yields [Ru5PtC(CO)16] (1) and the new compound [PPN]2[Ru10Pt2C2(CO) 28] (2), while, in a related reaction, [Ru6C(CO)16]2- undergoes addition of [PtCl2(MeCN)2] to yield the cluster [Ru12PtC2(CO)32- (MeCN)2] (3). The high nuclearity compounds 2 and 3 have been fully characterized and their structures determined by single crystal X-ray analysis. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003

High yield synthesis of Ru-Pt mixed-metal cluster compounds

The reaction of [PPN]2[Ru5C(CO)14] 1 or [PPN]2[Ru6C(CO)16] 2 [PPN+ = (PPh3)2N+] with Pt(II) compounds of general formula [PtX2Cl2] [X2 = (COD), (PPh3)2 and (PPh3)(CO)] (COD= 1,5-cyclooctadiene) have been investigated and the products of simple or double addition, viz. [Ru5PtC(CO)14(COD)] 3, [Ru5PtC(CO)14(PPh3)2] 4, [Ru5PtC(CO)15(PPh3)] 5, [Ru5Pt2C(CO)15(PPh3)2] 6, [Ru6PtC(CO)16(COD)] 7, [Ru6Pt2C(CO)15(COD)2] 8, obtained. The molecular and crystal structures of 3-8 have been established by single crystal X-ray analysis. Compounds 3-7 all contain an intact Ru core with Pt fragment(s) capping triangular or square faces. The resulting mixed-metal core is octahedral for the clusters Ru5Pt and face-capped octahedral for the clusters RunPtm (n = 5 or 6; m = 2 or 1). Only compound 8 did not follow this pattern, with the Pt fragments bridging two Ru-Ru edges of the otherwise unaltered Ru6C core

The synthesis and characterisation of the cluster dianion [PtRu5C(CO)15]2- and its reactions with Au and Pt cationic fragments produced in situ

The neutral mixed-metal cluster [PtRu5C(CO)16] was reduced by KOH in methanol to give [Ph4P]2 [PtRu5C(CO)15] 1 in 84% yield. Reaction of 1 with Au(PPh3)Cl afforded the gold derivative [PtRu5C(CO)15(AuPPh3)2] 2. Other reactions of 1 with [Pt(COD)Cl2] and [Pt(CO)(PPh3)Cl2] in the presence of silica yielded the new mixed-metal cluster compounds [Pt2Ru4C(CO)13(COD)] 3, [Ph4P]2[Pt3Ru10C2 (CO)32] 4, [Pt4Ru5C(CO)16(PPh3)3] 5, [PtRu4C(CO)13 (PPh3)] 6 and [Pt2Ru4C(CO)14(PPh3)] 7. Compounds 1-7 were characterised spectroscopically and the molecular and crystal structures of compound 1-5 were determined by single crystal X-ray crystallography

Single-step, highly active, and highly selective nanoparticle catalysts for the hydrogenation of key organic compounds

Pores for cluster catalysts: Nanoparticles of both Ru5Pt and Ru10Pt2, uniformly distributed along the inner walls of mesoporous silica, exhibit high catalytic performance in the single-step hydrogenation of dimethyl terephthalate (DMT, to 1,4-cyclohexanedimethanol (CHDM); see scheme), of benzoic acid (to cyclohexane carboxylic acid), and of naphthalene (in the presence of sulfur) to cisdecalin