Covalent bond 80 kcal, vander waals bond 0.5 kcal , ionic bond 40 kcal, and hydrogen bond 3 kcal is this right?
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bonded atoms. Molecular interactions are important in diverse fields of protein folding, drug design, material science, sensors, nanotechnology, separations, and origin of life. Molecular interactions are also known as noncovalent interactions or intermolecular interactions. Molecular interactions are not bonds.
Bonds hold atoms together within molecules. A molecule a set of atoms that associates tightly enough that it does not dissociate or lose its structure when it interacts with its environment. At room temperature two nitrogen atoms form a bond. Two argon atoms do not. Bonds break and form during chemical reactions. In the chemical reaction called fire, bonds of cellulose break while bonds of carbon dioxide and water form. Bond enthalpies are on the order of 100 kcal/mole (400 kjoule/mole), which is much greater than RT at room temperature, meaning that bonds do not break at room temperature.
Bonds remain intact and unchanged when (a) ice melts, (b) water boils, (c) carbon dioxide sublimes, (d) proteins unfold, (e) RNA unfolds, (f) DNA strands separate and (g) membranes disassemble. These processes of melting, boiling, sublimation, unfolding, strand separation and disassembly involve changes in molecular interactions, and are not chemical reactions (no bonds break or form). The enthalpy of a given molecular interaction, between a pair of non-bonded atoms, is 1 - 10 kcal/mole (4 - 42 kjoule/mole), which in the lower limit is on the order of RT and in the upper limit is significantly less than a covalent bond. Even though they are weak individually, cumulatively the energies of molecular interactions are significant.
Boiling Points. When a molecule transitions from the liquid to the gas phase (as during boiling), ideally all molecular interactions are disrupted. Differences in boiling temperatures give good qualitative indications of strengths of molecular interactions in the liquid phase. High boiling liquids have strong molecular interactions. The boiling point of H2O is hundreds of degrees greater than the boiling point of N2 because of stronger molecular interactions in H2O(liq) than in N2(liq). The forces between molecules in H2O(liq) are greater than those in N2(liq).
A2. Folding and assembly of biological macromolecules.
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Native states. In biological systems (i) proteins fold into globular structures called native states, (ii) ribosomal and transfer RNAs also fold into native globular structures, (iii) DNA forms double stranded helices, (iv) phospholipids form membranes, and (v) proteins assemble with DNA, RNA, membranes and with other proteins. These native states and assemblies are stabilized by molecular interactions of enormous number and complexity. Native states have low conformational entropy, which is a destabilizing influence.

Figure 1 shows the folding of a protein. Protein folding is the conversion from a denatured state (a random coil) to a native state. On the right-hand side the arrows are β-strands and the coils are α-helices.
Bonds hold atoms together within molecules. A molecule a set of atoms that associates tightly enough that it does not dissociate or lose its structure when it interacts with its environment. At room temperature two nitrogen atoms form a bond. Two argon atoms do not. Bonds break and form during chemical reactions. In the chemical reaction called fire, bonds of cellulose break while bonds of carbon dioxide and water form. Bond enthalpies are on the order of 100 kcal/mole (400 kjoule/mole), which is much greater than RT at room temperature, meaning that bonds do not break at room temperature.
Bonds remain intact and unchanged when (a) ice melts, (b) water boils, (c) carbon dioxide sublimes, (d) proteins unfold, (e) RNA unfolds, (f) DNA strands separate and (g) membranes disassemble. These processes of melting, boiling, sublimation, unfolding, strand separation and disassembly involve changes in molecular interactions, and are not chemical reactions (no bonds break or form). The enthalpy of a given molecular interaction, between a pair of non-bonded atoms, is 1 - 10 kcal/mole (4 - 42 kjoule/mole), which in the lower limit is on the order of RT and in the upper limit is significantly less than a covalent bond. Even though they are weak individually, cumulatively the energies of molecular interactions are significant.
Boiling Points. When a molecule transitions from the liquid to the gas phase (as during boiling), ideally all molecular interactions are disrupted. Differences in boiling temperatures give good qualitative indications of strengths of molecular interactions in the liquid phase. High boiling liquids have strong molecular interactions. The boiling point of H2O is hundreds of degrees greater than the boiling point of N2 because of stronger molecular interactions in H2O(liq) than in N2(liq). The forces between molecules in H2O(liq) are greater than those in N2(liq).
A2. Folding and assembly of biological macromolecules.
| Table of Contents | Structure | Williams Home |
Native states. In biological systems (i) proteins fold into globular structures called native states, (ii) ribosomal and transfer RNAs also fold into native globular structures, (iii) DNA forms double stranded helices, (iv) phospholipids form membranes, and (v) proteins assemble with DNA, RNA, membranes and with other proteins. These native states and assemblies are stabilized by molecular interactions of enormous number and complexity. Native states have low conformational entropy, which is a destabilizing influence.

Figure 1 shows the folding of a protein. Protein folding is the conversion from a denatured state (a random coil) to a native state. On the right-hand side the arrows are β-strands and the coils are α-helices.
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