The structures of the three major classes of biopolymers-polynucleotides, polypeptides and polysaccharides-are surveyed in the light of the most recent results from X-ray diffraction, electron microscopy and other studies. The review contains an introductory section setting out the basic features of each class of biopolymer: the natures of the 'building blocks', the linkages between them, conformational principles, types of repeating (secondary) structures and so on. The main section on each class is deliberately selective, because of the large amount of structural information now available. The section on polynucleotides concentrates on DNA, reviewing the classical double-helical models and the evidence provided by X-ray fibre diffraction, but also paying special attention to the rapid growth of new information on such features as the variations in helix geometry and in base-stacking, those data being derived primarily from studies of small self-complementary oligonucleotides. Alternative models and the question of right-handed versus left-handed structures are also considered. Among polypeptide structures, both globular and fibrous proteins are described. Globular proteins are treated as a group, with no detailed description of any one of them; this section concentrates on the organisation of globular proteins via folding units and domains, some general features (protein homology, catalysis, flexibility, interaction with water), membrane proteins, immunoglobulins and viruses.

REVIEW ARTICLE: Biopolymers

DNA has become one of the most extensively used molecular building blocks for engineering self-assembling materials. DNA origami is a technique that uses hundreds of short DNA oligonucleotides, called staple strands, to fold a long single-stranded DNA, which is called a scaffold strand, into various designer nanoscale architectures. DNA origami has dramatically improved the complexity and scalability of DNA nanostructures. Due to its high degree of customization and spatial addressability, DNA origami provides a versatile platform with which to engineer nanoscale structures and devices that can sense, compute, and actuate. These capabilities open up opportunities for a broad range of applications in chemistry, biology, physics, material science, and computer science that have often required programmed spatial control of molecules and atoms in three-dimensional (3D) space. This review provides a comprehensive survey of recent developments in DNA origami structure, design, assembly, and directed self-assemb...

DNA Origami: Scaffolds for Creating Higher Order Structures

Conformation of two-stranded DNA in H2O–methanol, H2O–ethanol, H2O–isopropanol, and H2O–dioxane solutions at different concentrations of alkaline ions has been studied with the aid of circular dichroism. The following conclusions are drawn:

The conformation of DNA in H2O and H2O–methanol belongs to a family of B forms (B, C, T forms are the representatives of the family). The magnitude of the winding angle between adjacent base pairs (θ) is determined by the concentration and type of the cations. In H2O the cation action is nonspecific and leads to an increase in θ value. In 80% methanol the ions act specifically, Cs+ being to stabilize a form with a greater θ value, and Li+ being with a lesser one. The total θ change is likely within the limits of 33° ⩽ θ ⩽ 45°.

At high content of ethanol, isopropanol, or dioxane (∼80%), but not with methanol, and in low ionic strength the conformation of DNA belongs to a family of A forms (A form is one of the members of the family) and is specified by the concentration and type of cation involved. The two-stranded regions of RNA in H2O are also of A type and winds with the rise of cation concentration. The range of θ variation is not narrower than 30° ⩽ θ 33°.

The conformational transitions within the families (induced by ions) are of non-cooperative pattern, wheras the transitions between the families (induced by nonpolar component) are of cooperative pattern. The effect of cations, when specific, is discussed on the basis of steric correspondence between the width of DNA narrow groove and the size of a hydrated cation.

Different conformations of double‐stranded nucleic acid in solution as revealed by circular dichroism

Meldola Lecture. The role of aromatic interactions in molecular recognition

Although a multitude of promising anti-cancer drugs have been developed over the past 50 years, effective delivery of the drugs to diseased cells remains a challenge. Recently, nanoparticles have been used as drug delivery vehicles due to their high delivery efficiencies and the possibility to circumvent cellular drug resistance. However, the lack of biocompatibility and inability to engineer spatially addressable surfaces for multi-functional activity remains an obstacle to their widespread use. Here we present a novel drug carrier system based on self-assembled, spatially addressable DNA origami nanostructures that confronts these limitations. Doxorubicin, a well-known anti-cancer drug, was non-covalently attached to DNA origami nanostructures through intercalation. A high level of drug loading efficiency was achieved, and the complex exhibited prominent cytotoxicity not only to regular human breast adenocarcinoma cancer cells (MCF 7), but more importantly to doxorubicin-resistant cancer cells, inducing...

DNA origami as a carrier for circumvention of drug resistance.

DAUNOMYCIN1–3, a glycosidic anthracycline antibiotic from Streptomyces peucetius4, is being used in the treatment of acute leukaemia and solid tumours in man5,6. The biological activity seems to be due to complex formation with the DNA of deoxyribonucleoprotein4. In vivo, daunomycin inhibits both RNA and DNA synthesis7,8 and, in vitro, DNA-dependent RNA polymerase and DNA polymerase7–9.

Stereochemistry of intercalation: interaction of daunomycin with DNA.

Unwinding the DNA helix by intercalation

X-RAY observations on a crystalline preparation of tRNAMetF from E coli have recently been reported1 The specimen consisted of an unoriented array of microcrystals and the crystalline X-ray reflexions extended to approximately 25 A The crystallization shows that this tRNA has a well defined structure, and raises the prospect of making crystals of suitable quality for detailed X-ray analysis It may be that such improvement in the crystallinity will require some time and effort, however, and therefore interpretations of the diffraction data will have to be attempted using information from other sources about tRNA The clover leaf structure of tRNA2 might be taken as a starting point and information on the arrangement of the various arms used to construct a first trial model the structure and packing of which in the unit cell can then be refined to give the best agreement with the crystalline tRNA X-ray data

Arrangement of the helical regions in E. coli tyrosine tRNA.

RNA can exist in three distinct forms, all with a similar structure to that of the A form of DNA. The possible biological significance of these structures in protein synthesis and transcription mechanisms is discussed.

Molecular conformations and structure transitions of RNA complementary helices and their possible biological significance.

Structures of synthetic polynucleotides in the A-RNA and A'-RNA conformations: x-ray diffraction analyses of the molecular conformations of polyadenylic acid--polyuridylic acid and polyinosinic acid--polycytidylic acid.

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