1. HYDROGEN BONDS IN DNA NHO Distance between the N and O Covalent bond hydrogen bond Bond angle between N, H and O

2. NHO HYDROGEN BONDS IN DNA N H N H N O C GA T H N O N H N

3. HYDROGEN BONDS IN DNA The factors affecting the strength of a hydrogen bond are: - interatomic distances - directionality - linearity For instance, for calculating the H-bond between N-H and O we can use the folowing expression (Kcal/mol): Where (R NO) is the actual distance between the N and O atom A collinear configuration of the three atoms would have the lowest potencial energy

4. HYDROGEN BONDS IN DNA Hidrogen bond energy between N-H and O when: = 180º

5. The "H-bond effect" is an extremely important factor (by sheer numbers!) in intermolecular attraction & has a profound effect on many chemical & physical properties of organic compounds with OH, NH HYDROGEN BONDS IN DNA

6. In biochemistry, inter-molecular H bonds are crucial for specific molecular recognition and intra- molecular H bonds are important in the maintenance of the 3-D structures HYDROGEN BONDS IN DNA