It is a less invasive surgery, so your recovery time is shorter and easier than with mastectomy. Lumpectomy has a few potential disadvantages: You are likely to have 5 to 7 weeks of radiation therapy, 5 days per week, after lumpectomy surgery to make sure the cancer is gone.
DNA: Double Helix. The secondary structure of DNA is actually very similar to the secondary structure of proteins. The protein single alpha helix structure held together by hydrogen bonds was discovered with the aid of X-ray diffraction studies. The X-ray diffraction patterns for DNA show somewhat similar patterns.
It is convenient to describe protein structure in terms of 4 different aspects of covalent structure and folding patterns. The different levels of protein structure are known as primary, secondary, tertiary, and quaternary structure. Primary Structure of Proteins The primary structure is the sequence of amino acids that make up a polypeptide chain. 20 different amino acids are found in proteins. The exact order of the amino acids in a specific protein is the primary sequence for that protein. Secondary Structure of Proteins Protein secondary structure refers to regular, repeated patterns of folding of the protein backbone. The two most common folding patterns are the alpha helix and the beta sheet. Alpha Helix. In an alpha helix, the polypeptide backbone coils around an imaginary helix axis in clockwise direction.