Co-operative non-enzymic base recognition. A kinetic study of interaction between GpGpGpC and GpCpCpC and of self-association of GpGpGpC

Rolling Circle Transcription for the Self-Assembly of Multimeric RNAi Structures and Its Applications in Nanomedicine

The enzymatic process of rolling circle transcription (RCT) enables self-assembly of multimeric RNAi structures from a circular DNA template. The self-assembled RNAi structures can be manipulated easily by simple base pairing rules with short DNA fragments for constructing multifunctional nanoparticles in the field of nanomedicine. Here we describe the method to generate multifunctional RNAi nanoparticles applicable in nanomedicine.

Rapid hybridization of nucleic acids using isotachophoresis

We use isotachophoresis (ITP) to control and increase the rate of nucleic acid hybridization reactions in free solution. We present a new physical model, validation experiments, and demonstrations of this assay. We studied the coupled physicochemical processes of preconcentration, mixing, and chemical reaction kinetics under ITP. Our experimentally validated model enables a closed form solution for ITP-aided reaction kinetics, and reveals a new characteristic time scale which correctly predicts order 10,000-fold speed-up of chemical reaction rate for order 100 pM reactants, and greater enhancement at lower concentrations. At 500 pM concentration, we measured a reaction time which is 14,000-fold lower than that predicted for standard second-order hybridization. The model and method are generally applicable to acceleration of reactions involving nucleic acids, and may be applicable to a wide range of reactions involving ionic reactants.

Antibody-nucleic acid complexes. Oligo(dG)n and -(dT)n specificities associated with anti-DNA antibodies from autoimmune MRL mice

The specificity of anti-DNA antibodies in the sera of unimmunized autoimmune MRL mice was initially assessed via an enzyme-linked immunosorbent assay (ELISA). Antibody binding profiles to a panel of immobilized antigens (AMP-, GMP-, CMP-, UMP-, and TMP-BSA, ss- and dsDNA) demonstrated high levels of immunoglobulins reacting with GMP and ssDNA and intermediate levels with AMP, TMP, and dsDNA. Fractionation of serum anti-DNA antibodies into subsets on the basis of their binding to GMP- and TMP-agarose indicated that the resulting GMP- or TMP-reactive antibodies bound to their homologous nucleotides and ssDNA. Competition-inhibition studies with soluble mono-, oligo-, and polynucleotides revealed that GMP- and TMP-reactive antibodies were highly specific for oligo(dG)n and -(dT)n sequences, respectively. Whereas the relative affinity of TMP-reactive autoantibodies to oligo(dT)n increased with oligonucleotide length (n = 2, 4, 6, 8, 10, 15), GMP-reactive antibodies preferentially recognized oligo(dG)10 (Ka congruent to 1 x 10(7) M-1). While neither antibody recognized oligo(dA)8 and -(dC)8 competitors, mixed-base oligonucleotides were inhibitory at concentrations approximately 10-fold greater than similarly sized oligo(dG)n and -(dT)n sequences. Similar characterizations of both pooled and individual MRL sera indicated that anti-DNA antibodies represent 8-10% of the total serum IgG. More importantly, GMP-reactive autoantibodies predominated and accounted for 60-70% of the entire unbound anti-DNA antibody population.

Specificity of anti-nucleoside antibodies in systemic lupus erythematosus

The titer of IgG antinucleoside antibodies in the sera of 162 individuals was determined by an enzyme-linked immunosorbent assay. The nucleosides used in the assay were adenosine, cytidine, guanosine, and thymine-riboside conjugated to human serum albumin. The specificity of IgG antinucleoside antibodies was indicated by appropriate reduction in antibody binding after solid-phase adsorptions of antibody with specific immobilized nucleoside conjugates. Disease-associated increases in serum IgG antibodies to cytidine and guanosine but not to adenosine or thymine-riboside occurred in patients with systemic lupus erythematosus (SLE). The epitope density of nucleosides in the conjugates and differences in the sensitivity of each nucleoside assay were not responsible for disease-associated IgG antinucleoside antibody responses. These findings support a possible pathogenic role for cytidine and guanosine as antigens or crossreactive antigenic determinants in some patients with SLE.