Ribonucleic acid (RNA) plays a crucial role in the genetics of organisms and is essential for the origin and evolution of life on our planet. A recent study published in the journal Proceedings of the National Academy of Sciences sheds light on how RNA folding at low temperatures can provide a new perspective on primordial biochemistry and the evolution of life. Led by Professor Fèlix Ritort and his team from the University of Barcelona, the research explores the intricate structures formed by RNA molecules and their implications for the biological functions of these molecules.
RNA is composed of ribose molecules linked to phosphate groups and nitrogenous bases such as adenine, guanine, cytosine, and uracil. The sequence and three-dimensional structure of RNA play a significant role in its biological functions. Through mechanical unfolding of RNA, researchers have uncovered the diverse forms that RNA takes when it folds in on itself. Professor Fèlix Ritort emphasizes the importance of structure in biological molecules, stating that without structure, there is no function, and without function, there is no life. The study reveals that RNA sequences forming hairpin structures adopt compact structures at low temperatures, with a range of stability between +20°C and -50°C.
The research suggests that RNA stability at low temperatures is influenced by ribose-water interactions, reaching a maximum stability at +5°C. Below this temperature, the stability of RNA is determined by ribose-water interactions until -50°C when the RNA unfolds, leading to cold denaturation. This phenomenon of RNA stability at low temperatures is believed to be universal across all RNA molecules but can be modulated by sequence and environmental conditions like salt and acidity. These new RNA structures are stabilized by hydrogen bonds between ribose and water, altering the traditional rules of RNA biochemistry based on A-U and G-C pairing.
The team employed optical tweezer force spectroscopy, a precise technique for measuring molecular thermodynamics, to study RNA folding at low temperatures. By measuring entropy changes and heat capacity during the folding of different RNAs, the researchers detected a decrease in heat capacity around 20°C, indicating a reduction in degrees of freedom in folded RNA due to ribose-water bonds. This innovative technique has provided valuable insights into the structural changes and thermodynamics of RNA molecules at cold temperatures.
The altered biochemistry of RNA folding observed at low temperatures has significant implications for organisms inhabiting cold environments, such as psychrophiles. The dominance of ribose-water interactions suggests the existence of a primitive biochemistry based on ribose and other sugars, predating the traditional A-U and G-C pairing rules in RNA. This concept, termed the sweet-RNA world, proposes a primitive form of biochemistry that may have originated in cold environments in outer space, subjected to thermal cycles.
The study on RNA folding at low temperatures provides a new perspective on the evolution of life and the role of RNA in biological functions. The discovery of novel RNA structures and the implications of ribose-water interactions challenge the conventional rules of RNA biochemistry and suggest a primitive form of biochemistry in cold environments. This research opens new avenues for exploring the origins of life and the potential impact of environmental conditions on the evolution of RNA molecules.
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