Binding of the plant alkaloid aristololactam-β-d-glucoside and antitumor antibiotic daunomycin to single stranded polyribonucleotides

Small molecule-RNA recognition: Binding of the benzophenanthridine alkaloids sanguinarine and chelerythrine to single stranded polyribonucleotides

Single stranded RNAs are biologically potent as they participate in various key cellular processes. The binding efficacy of two potent anticancer alkaloids, sanguinarine (here after SANG) and chelerythrine (here after CHEL), with single-stranded ribonucleic acids poly(rI), poly(rG), and poly(rC) were studied using spectroscopic and thermodynamic tools. Results reveal that both SANG and CHEL binds well with single stranded RNAs with affinity in the order poly(rI)>poly(rG)>poly(rC). CHEL showed slightly higher affinity compared to SANG with all the single stranded RNAs. Both SANG and CHEL showed association affinity of the lower 10⁶ order with poly(rI), higher 10⁵ order binding with poly(rG) and lower 10⁵ order with poly(rC). The binding mode was partial intercalation due to the staking interaction between the bases and the alkaloids. The complexation of both the SANG and CHEL to the RNAs were mainly enthalpy driven and also favoured by entropy changes. Perturbation was observed in the RNA conformation due to binding of the alkaloids. In this present study we have deciphered the fundamental structural and calorimetric aspects of the interaction of the natural benzophenanthridine alkaloids with single stranded RNAs and these results may help to develop new generation alkaloid based therapeutics targeting single stranded RNAs.

The use of calorimetry in the biophysical characterization of small molecule alkaloids binding to RNA structures

BACKGROUND

RNA has now emerged as a potential target for therapeutic intervention. RNA targeted drug design requires detailed thermodynamic characterization that provides new insights into the interactions and this together with structural data, may be used in rational drug design. The use of calorimetry to characterize small molecule-RNA interactions has emerged as a reliable and sensitive tool after the recent advancements in biocalorimetry.

SCOPE OF THE REVIEW

This review summarizes the recent advancements in thermodynamic characterization of small molecules, particularly some natural alkaloids binding to various RNA structures. Thermodynamic characterization provides information that can supplement structural data leading to more effective drug development protocols.

MAJOR CONCLUSIONS

This review provides a concise report on the use of isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) techniques in characterizing small molecules, mostly alkaloids-RNA interactions with particular reference to binding of tRNA, single stranded RNA, double stranded RNA, poly(A), triplex RNA.

GENERAL SIGNIFICANCE

It is now apparent that a combination of structural and thermodynamic data is essential for rational design of specific RNA targeted drugs. Recent advancements in biocalorimetry instrumentation have led to detailed understanding of the thermodynamics of small molecules binding to various RNA structures paving the path for the development of many new natural and synthetic molecules as specific binders to various RNA structures. RNA targeted drug design, that remained unexplored, will immensely benefit from the calorimetric studies leading to the development of effective drugs for many diseases.

New 13-pyridinealkyl berberine analogues intercalate to DNA and induce apoptosis in HepG2 and MCF-7 cells through ROS mediated p53 dependent pathway: biophysical, biochemical and molecular modeling studies

A new series of 13-pyridinealkyl berberine analogues was synthesized and their DNA binding efficacy studied by employing spectroscopic, calorimetric and molecular modeling techniques.

Targeting double-stranded RNA with spermine, 1-naphthylacetyl spermine and spermidine: a comparative biophysical investigation

RNA targeting is an evolving new approach to anticancer therapeutics that requires identification of small molecules to selectively target specific RNA structures. In this report, the interaction of biogenic polyamines spermine, spermidine and the synthetic analogue 1-naphthylacetyl spermine with three double-stranded RNA polynucleotides--poly(I)·poly(C), poly(C)·poly(G), and poly(A)·poly(U)--has been described to understand the structural and thermodynamic basis of the binding and the comparative efficacy of the analogue over the natural polyamines. Circular dichroism spectroscopy, thermal melting experiments, and ethidium bromide displacement assay were used to characterize the interaction. Microcalorimetry studies were performed to deduce the energetics of the interaction and atomic force microscopy experiments done to gain insight into the interaction at the molecular level. The experiments demonstrated structural perturbations in the polynucleotides on binding of the polyamines. Thermal melting studies showed enhanced stabilization of RNA-polyamine complexes with increase in the total standard molar enthalpy of transition. The binding affinity was strongest for poly(I)·poly(C) as revealed by microcalorimetry results and varied as poly(I)·poly(C) > poly(C)·poly(G) > poly(A)·poly(U). The order of affinity for the polyamines was spermine >1-naphthylacetyl spermine > spermidine. Total enthalpy-entropy compensation and high standard molar heat capacity values characterized the interactions. The results of the study on the binding of polyamines to dsRNAs presented here have been compared to those reported earlier with dsDNAs. The present findings advance our knowledge on the mechanism of interaction of polyamines with RNA and may help in the search for analogues that can interfere with biogenic polyamine metabolism and function.

Comprehensive review on additives of topical dosage forms for drug delivery

Skin is the largest organ of the human body and plays the most important role in protecting against pathogen and foreign matter. Three important modes such as topical, regional and transdermal are widely used for delivery of various dosage forms. Among these modes, the topical dosage forms are preferred because it provides local therapeutic activity when applied to the skin or mucous membranes. Additives or pharmaceutical excipients (non-drug component of dosage form) are used as inactive ingredients in dosage form or tools for structuring dosage forms. The main use of topical dosage form additives are controling the extent of absorption, maintaining the viscosity, improving the stability as well as organoleptic property and increasing the bulk of the formulation. The overall goal of this article is to provide the clinician with information related to the topical dosage form additives and their current major applications against various diseases.

Binding studies of aristololactam-β-d-glucoside and daunomycin to human serum albumin

The binding of two carbohydrate containing molecules aristololactam-β-d-glucoside and daunomycin with human serum albumin was evaluated by biophysical techniques.