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Spider dragline silk possesses impressive mechanical and biochemical properties. It is synthesized by a couple of major ampullate glands in spiders and comprises of two major structural proteins--spidroins 1 and 2. The relationship between structure and mechanical properties of spider silk is not well understood. Here, we modeled the complete process of the spider silk assembly using two new recombinant analogs of spidroins 1 and 2. The artificial genes sequence of the hydrophobic core regions of spidroin 1 and 2 have been designed using computer analysis of existing databases and mathematical modeling. Both proteins were expressed in Pichia pastoris and purified using a cation exchange chromatography. Despite the absence of hydrophilic N- and C-termini, both purified proteins spontaneously formed the nanofibrils and round micelles of about 1 microm in aqueous solutions. The electron microscopy study has revealed the helical structure of a nanofibril with a repeating motif of 40 nm. Using the electrospinning, the thin films with an antiparallel beta-sheet structure were produced. In summary, we were able to obtain artificial structures with characteristics that are perspective for further biomedical applications, such as producing three-dimensional matrices for tissue engineering and drug delivery.

On the basis of complete scanning through conformational space of dihedral angles, twelve structural genera were obtained. Subsequent energy minimization within these genera yielded a limited set of duplexes with stacking: right-handed B-form (Wilkins type), B2-form (Watson and Crick type) and left-handed Ll-form (Sasisekharan type) and the new L2-form. In the polymeric DNA only right-handed double-helices are possible, the left-handed helices are forbidden due to poor 1–5 interchain contacts. In contrast, for short fragments the left- and right-handed helicek have practically the same energies providing some physical ground for side-by-side form, which biologically is possible as recombination form and may be as replication form.

A possible code is suggested that describes a correspondence between amino acid sequences in stereospecific sites of regulatory proteins and nucleotide sequences at the control sites on DNA. Stereospecific sites of regulatory proteins are assumed to contain pairs of antiparallel polypeptide chain segments which form a right-hand twisted antiparallel beta-sheet with single-stranded regions at the ends of the beta-structure. The binding reaction between regulatory protein and double-helical DNA is accompanied by significant structural alterations at stereospecific sites of the protein and DNA. Half of the hydrogen bonds normally existing in beta-structure are broken upon complex formation with DNA and a new set of hydrogen bonds is formed between polypeptide amide groups and DNA base pairs. The code states a correspondence between four amino acid residues at a stereospecific site of the regulatory protein and an AT (GC) base pair at the control site. It predicts that there are six fundamental amino acid residues (serine, threonine, histidine, asparagine, glutamine and cysteine) whose arrangement in the stereospecific site determines the base pair sequence to which a given regulatory protein would bind preferentially.