Homochirality and Principle of Chirality Hierarchy. The cooperativity effect also exists in homochiral systems. Homochirality, i.e., the uniformity of chirality, is the propensity of a molecular system for all its chiral centers to assume the same chirality. It is a striking yet common feature of amino acids in proteins and carbohydrates in DNA. In a recent study, we discovered that that homochirality of amino acids and nucleotide sugars originates from the handedness of helices. The right-handed 310-helix and -helix favor the L-chiral form for amino acids, but for deoxyribose sugars it is the right-handed DNA helix that dictates carbohydrates taking the D-chiral form. We found that there exists strong cooperativity effect in these systems, which are dominated by the electrostatic interaction. As shown in Fig. , 310-helix is negatively cooperative, but -helix is positively cooperative. This opposite behavior in cooperativity between these two types of helixes explains why -helixes are predominant in nature and 310-helixes are scarce. In the two single-stranded DNA models, cooperativity is always positive. We recently validated these results in three-blade propeller systems. These results eluded us to propose the Principle of Chirality Hierarchy, which states that chirality of a lower hierarchy is dictated by that of higher ones. There are different types of chirality in molecular systems, such as 0D (point) chirality, 1D (axial) chirality, 2D (planar) chirality, and 3D chirality. When different kinds of chirality are included in one system, a chirality hierarchy will be formed. For example, the right-handed helical structure is 1D chirality, the Cα atom of amino acid residues except glycine is 0D chiral, so 310 and α helixes form a chirality hierarchy containing two kinds of chirality, 0D and 1D. Applying the above PCH, we know that the Lhomochiral form of amino acids is dictated by helix's right-handedness, i.e., 1D chirality.