In the '60s, Löwdin explored the realm of Quantum Biology. Löwdin defined Quantum Biology as the use of quantum mechanics to study the activity and molecular properties of biologically active molecules such as DNA, RNA, and proteins. This dissertation aims to describe molecules of biological interest such as DNA base pairs and amyloid-beta peptides and treat them using a quantum mechanical approach. We used electronic structure methods to achieve the quantum biological nature of these molecules under our computational power, tools, and techniques. In chapter 2, we present the quantum mechanical description of the spontaneous mutations in DNA base pairs using Wigner's tunneling corrections. We demonstrated that tunneling corrections are essential for the mutation description, where the GC complex is more likely to mutate, showing a larger mutation rate in a low polarity media. Following the principles of quantum biology, in chapter 3 and chapter4, we provide a compressive study on the amyloid- beta 1-42 (Aβ1-42) and Aβ25-35 fibril formation, respectively. Our findings show that the monomers present an L-S and hairpin-like topology, respectively, and an intense out of the plane dipole moment. The protofibrils present a perfectly axial dipole moment centered in the center of the pore-like structure. Based on our findings, we hypothesize that the aggregation mechanism is electric dipole assisted and follows a nucleated polymerization and a conformational conversion route, respectively. In chapter 5, we introduce the calcium ion-channel capability of Aβ1-42 and Aβ25-35 peptides using molecular dynamics simulations. Our research demonstrated that both peptides could form ion-conducting channels. Though in the case of Aβ1-42, only the protofibrils can create the channels in the gas, condensate, and membrane incrusted conditions, while Aβ25-35 can only form channels in its monomeric form. The recent results show an additional pathway for cytotoxicity in Alzheimer's disease that agrees with experimental findings.
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Doctor of Philosophy (Ph.D.)
College of Sciences
Length of Campus-only Access
Doctoral Dissertation (Campus-only Access)
Romero Camacho, Eduardo, "Quantum Biology? From DNA Point Mutations to Fibril Formation in Alzheimer Disease" (2020). Electronic Theses and Dissertations, 2020-. 125.