Biomedical subjects

S C Zimmerman

Publications and source records attributed to S C Zimmerman.

6 recordsLinked to original sources

PubMed1998

Applications of dendrimers in bio-organic chemistry.

Dendrimers represent a new class of highly branched polymers whose interior cavities and multiple peripheral groups facilitate potential applications in biomedicine and bio-organic chemistry. Major advances in the past year were made in the synthesis and study of new carbohydrate, nucleic acid, and peptide dendrimers, as well as in the use of dendrimers as magnetic resonance imaging contrast agents, as agents for cellular delivery of nucleic acids, and as scaffolds for biomimetic systems.

Biochemical Phenomena↗

PubMed1996

Self-assembling dendrimers.

Hydrogen bond-mediated self-assembly is a powerful strategy for generating large structures from smaller subunits. The synthesis of molecules containing two isophthalic acid units covalently attached to a rigid aromatic spacer is described. By normal pairing of carboxylic acids into hydrogen-bonded dimers, these molecules self-assemble in organic solvents to form either a series of linear aggregates or a cyclic hexamer. These molecules were linked to the core of a family of polyether dendrimers, which caused the hexamer to be formed preferentially. The stability of the hexamer depended on the generation number of the dendrimer. The largest of these hydrogen-bonded macromolecular assemblies is roughly disk-shaped with a 9-nanometer diameter and a 2-nanometer thickness. Its size and molecular mass (34,000 daltons) are comparable to that of small proteins.

Carboxylic Acids↗

PubMed1996

Synthesis of heterocycles containing two cytosine or two guanine base-pairing sites. Novel tectons for self-assembly.

The synthesis of 1 and 2 is described, as is the X-ray structure of 1. Tecton 1 contains two DAA hydrogen bonding sites (cytosine-like), while 2 contains two DDA sites (guanosine-like). Tectons 1 and 2 were designed to self-assemble into a helical superstructure. Self-recognition of 1 occurs in the solid state with a novel inclusion of dimethylacetamide solvent.

Crystallography, X-Ray↗

PubMed1993

Chemically bonded stationary phases that use synthetic hosts containing aromatic binding clefts: HPLC analysis of nitro-substituted polycyclic aromatic hydrocarbons.

The synthesis of hosts with improved binding affinities for nitroaromatic guests is described. Association constants for several host-guest complexes were measured in chloroform solution and ranged over three orders of magnitude. Two hosts were covalently linked to silica gel to produce chemically bonded stationary phases for HPLC. The use of these phases for HPLC analysis of nitro-substituted polycyclic aromatic hydrocarbons is discussed.

Chromatography, High Pressure Liquid↗

PubMed1992

Structures of methyl 7-phenyldibenz[a,j]anthracene-14-carboxylate and methyl 7-phenylbenzo[1,2-h:5,4-h']diquinoline-14-carboxylate: twisted aromatic spacers containing bay-region esters.

C30H20O2, (1), Mr = 412.49, triclinic, P1 (Ci1), a = 11.301 (7), b = 12.069 (3), c = 9.777 (2) A, alpha = 96.12 (2), beta = 111.59 (4), gamma = 114.68 (3) degrees, V = 1072 (2) A3, Z = 2, Dx = 1.278 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 0.73 cm-1, F(000) = 432, T = 299 K, final R = 0.065 for 1231 observed reflections. C28H18N2O2, (2), Mr = 414.46, monoclinic, I2/a (C2h6), a = 20.039 (10), b = 11.762 (8), c = 19.850 (5) A, beta = 117.61 (3) degrees, V = 4146 (8) A3, Z = 8, Dx = 1.328 g cm-3, lambda(Mo K alpha) = 0.71073 A, mu = 0.79 cm-1, F(000) = 1728, T = 298 K, final R = 0.048 for 1924 observed reflections. Aromatic system (1) is highly twisted (43 degrees from end to end) in a helical sense. Half of aromatic system (2) is nearly planar with the ester C atom, whereas the other half is twisted by ca 27 degrees for planarity.

Benz(a)Anthracenes↗

PubMed1990

Interaction of a macrocyclic bisacridine with DNA.

The binding of the macrocycle SDM to DNA was investigated by visible spectroscopy, stopped-flow kinetics, and NMR spectroscopy. SDM is composed of two 9-aminoacridines linked via the amino groups by a spermine side chain and via the 4-positions by a N,N'-[(methylthio)ethyl]succinamide side chain [Zimmerman, S. C., Lamberson, C. R., Cory, M., & Fairley, T. A. (1989) J. Am. Chem. Soc. 111, 6805-6809]. The visible spectrum of SDM bound to poly[d(A-T)]2 or poly[d(G-C)]2 is red-shifted relative to the spectrum of SDM alone and displays considerable hypochromicity. Results from titrations of SDM with polymer indicate a binding site size of three base pairs per macrocycle. The dissociation constant for SDM bound to either poly[d(A-T)]2 or poly[d(G-C)]2 is an order of magnitude lower than that for a similar bisacridine linked only by a spermine side chain. In addition, the dependence of the dissociation constant on ionic strength is significantly reduced. NMR studies of SDM complexes with poly[d(A-T)]2 or a tetramer, d(CGCG)2, show that intercalation is the mode of binding. The magnitudes of the chemical shift differences for SDM aromatic protons in the free and bound states support intercalation with the acridine ring systems essentially parallel to the long axis of the base pairs. Cross peaks from NOESY spectra of the SDM complex with d(CGCG)2 further support this mode of binding and provide information on the structure of the complex. The results are analyzed for consistency with each of three binding models: (i) bisintercalation with the two side chains in the same groove; (ii) bisintercalation according to the neighbor-exclusion principle with the two side chains in opposite grooves; and (iii) bisintercalation with two side chains in opposite grooves but with violation of the neighbor-exclusion principle. Model i is found to be unlikely on the basis of all evidence obtained, including preliminary modeling studies. Both models ii and iii can be reconciled with the experimental evidence and from a modeling standpoint are energetically feasible.

Aminoacridines↗