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2015**

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Volume 15, Number 4, pp. 195–199**

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**Helix–coil transition in macromolecules with sequence heterogeneity**

**S.A. Tonoyan, ^{1} Z.A. Grigoryan,^{2} A.V. Asatryan^{1} and Y.S. Mamasakhlisov^{1}**

^{1}Yerevan State University, A. Manoogian 1, 0025 Yerevan, Armenia

^{2}Goris State University, Avangard 4, 3204 Goris, Armenia

We consider the theory of helix–coil transition in heterogeneous macromolecules with an arbitrary number of components in the case of heterogeneity with respect to both energy and number of conformations. The theory is based on the generalized model of a polypeptide chain (GMPC) employing the constrained annealing method. The expression for the free energy of the heteropolymer is derived using the averaged transfer matrix of homopolymer GMPC with redefined energy and conformation parameters. We show that bimodal heterogeneity determines qualitatively the basic properties of melting of a random heteropolymer. We also show that heterogeneity with respect to energy and heterogeneity with respect to number of conformations determine essentially the same characteristics of the melting curves.

**Keywords:** biopolymers, helix–coil transition, heterogeneity, melting curve

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