Madeleine Helliwell

Bio: Madeleine Helliwell is an academic researcher from University of Manchester. The author has contributed to research in topics: Crystal structure & Ring (chemistry). The author has an hindex of 54, co-authored 370 publications receiving 9898 citations. Previous affiliations of Madeleine Helliwell include University of Santiago de Compostela & Sheffield Hallam University.

Anion Induced Formation of Supramolecular Associations Involving Lone pair−π and Anion−π Interactions in Co(II) Malonate Complexes: Experimental Observations, Hirshfeld Surface Analyses and DFT Studies

Abstract: Three Co(II)–malonate complexes, namely, (C5H7N2)4[Co(C3H2O4)2(H2O)2](NO3)2 (1), (C5H7N2)4[Co(C3H2O4)2(H2O)2](ClO4)2 (2), and (C5H7N2)4[Co(C3H2O4)2(H2O)2](PF6)2 (3) [C5H7N2 = protonated 2-aminopyridine, C3H4O4 = malonic acid, NO3– = nitrate, ClO4– = perchlorate, PF6– = hexafluorophosphate], have been synthesized from purely aqueous media, and their crystal structures have been determined by single crystal X-ray diffraction. A thorough analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions in 1–3, which are crucial in building supramolecular architectures. When these complexes are structurally compared with their previously reported analogous Ni(II) or Mg(II) compounds, a very interesting feature regarding the role of counteranions has emerged. This phenomenon can be best described as anion-induced formation of extended supramolecular networks of the type lone pair−π/π–π/π–anion−π/π–lone pair and lone pair−π/π–π/π–anion involving various weak forces lik...

The chemical vapor deposition of nickel phosphide or selenide thin films from a single precursor

Abstract: Nickel phosphide, nickel selenide thin films and their heterostructure (Ni0.85Se/Ni2P) were deposited from a newly synthesized single source precursor {Ni[iPr2P(S)NP(Se)iPr2]2} just by altering the deposition temperature using CVD.

Ultra-remote stereocontrol by conformational communication of information along a carbon chain

Abstract: Many receptors1 and allosteric proteins2 function through binding of a molecule to induce a conformational change, which then influences a remote active site. In synthetic systems, comparable intramolecular information transfer can be effected by using the shape of one part of a molecule to control the stereoselectivity of reactions occurring some distance away3. However, the need for direct communication with the reaction site usually limits such remote stereocontrol to distances of not more than about five bond lengths. Cyclic structures overcome this problem by allowing the controlling centre and the reaction site4,5 to approach each other, but the information transfer spans only short absolute distances. Truly remote stereocontrol can, however, be achieved with rigid compounds containing amide groups: the conformation of the amides can be controlled by stereogenic centres6,7,8,9 and responds to that of neighbouring amide groups10,11,12 and in turn influences stereoselective reactions13. This strategy has allowed remote stereocontrol spanning 8 (ref. 11) or 9 (ref. 12) bonds. Here we demonstrate stereocontrol over a reaction taking place more than 20 bond lengths from the controlling centre, corresponding to a linear distance of over 2.5 nm. This transmission of information, achieved by conformational changes relayed through the molecule, provides a chemical model of allostery and might serve as a molecular mechanism for communicating and processing information14,15,16.

Heme-like coordination chemistry within nanoporous molecular crystals

Abstract: Crystal engineering of nanoporous structures has not yet exploited the heme motif so widely found in proteins. Here, we report that a derivative of iron phthalocyanine, a close analog of heme, forms millimeter-scale molecular crystals that contain large interconnected voids (8 cubic nanometers), defined by a cubic assembly of six phthalocyanines. Rapid ligand exchange is achieved within these phthalocyanine nanoporous crystals by single-crystal–to–single-crystal (SCSC) transformations. Differentiation of the binding sites, similar to that which occurs in hemoproteins, is achieved so that monodentate ligands add preferentially to the axial binding site within the cubic assembly, whereas bidentate ligands selectively bind to the opposite axial site to link the cubic assemblies. These bidentate ligands act as molecular wall ties to prevent the collapse of the molecular crystal during the removal of solvent. The resulting crystals possess high surface areas (850 to 1000 square meters per gram) and bind N2 at the equivalent of the heme distal site through a SCSC process characterized by x-ray crystallography.

Synthetic and structural studies of cobalt-pivalate complexes.

Abstract: The synthesis and characterisation of a range of cobalt pivalate cage complexes are reported. The cages include: a dinuclear Co I I complex; an oxo-centred Co I I I triangle; tetranuclear Co I I heterocubanes and butterflies; tetranuclear heterovalent cobalt butterflies and hexanuclear edge-sharing bitetrahedra; heterovalent penta-, hexa- and hepta-nuclear cages based on {M 4 O 4 } heterocubane cores; and a tetradecanuclear cage based on heterocubanes sharing edges and vertices. Spectroscopic studies suggest that some of these cores are retained in solution, but that only in the Co I I I triangle is the structure including ligands retained. A scheme is proposed to account for the many structures observed, which may be applicable to other polymetallic cage complexes.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

The Chemistry and Applications of Metal-Organic Frameworks

Abstract: Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

Synthetic molecular motors and mechanical machines.

Abstract: The widespread use of controlled molecular-level motion in key natural processes suggests that great rewards could come from bridging the gap between the present generation of synthetic molecular systems, which by and large rely upon electronic and chemical effects to carry out their functions, and the machines of the macroscopic world, which utilize the synchronized movements of smaller parts to perform specific tasks. This is a scientific area of great contemporary interest and extraordinary recent growth, yet the notion of molecular-level machines dates back to a time when the ideas surrounding the statistical nature of matter and the laws of thermodynamics were first being formulated. Here we outline the exciting successes in taming molecular-level movement thus far, the underlying principles that all experimental designs must follow, and the early progress made towards utilizing synthetic molecular structures to perform tasks using mechanical motion. We also highlight some of the issues and challenges that still need to be overcome.

Nanoparticles, Proteins, and Nucleic Acids: Biotechnology Meets Materials Science

Abstract: Based on fundamental chemistry, biotechnology and materials science have developed over the past three decades into today's powerful disciplines which allow the engineering of advanced technical devices and the industrial production of active substances for pharmaceutical and biomedical applications. This review is focused on current approaches emerging at the intersection of materials research, nanosciences, and molecular biotechnology. This novel and highly interdisciplinary field of chemistry is closely associated with both the physical and chemical properties of organic and inorganic nanoparticles, as well as to the various aspects of molecular cloning, recombinant DNA and protein technology, and immunology. Evolutionary optimized biomolecules such as nucleic acids, proteins, and supramolecular complexes of these components, are utilized in the production of nanostructured and mesoscopic architectures from organic and inorganic materials. The highly developed instruments and techniques of today's materials research are used for basic and applied studies of fundamental biological processes.