Mathematics, thermodynamics, and modeling to address ten common misconceptions about protein structure, folding, and stability

Probing the Interactions Responsible for the Structural Stability of Trypanothione Reductase Through Computer Simulation and Biophysical Characterization

With the necessity to develop antileishmanial drugs with substrate specificity, trypanothione reductase (TryR) has gained popularity in parasitology. TryR is unique to be present only in trypanosomatids and is functionally similar to glutathione in mammals. It protects against oxidative stress exerted by the host defense mechanism. The TryR enzyme is essential for the survival of Leishmania parasites in the host as it reduces trypanothione and aids in neutralizing hydrogen peroxide produced by the host macrophages during infection. Henceforth, it becomes vital to decipher their functional stability and behaviour in the presence of denaturants. Our study is focused on structural, functional and behavioural stability aspects of TryR with different concentrations of Urea, Guanidinium chloride, alcohol based compounds followed by extensive molecular dynamics simulations in a lipid bilayer system. The results obtained from the study reveal an interesting insight into the possible mechanisms of modulation of the structure, function and stability of the TryR protein.

Using Molecular Visualisation Techniques to Explain the Molecular Biology of SARS-CoV-2 Spike Protein Mutations to a General Audience

Since the COVID-19 pandemic started in 2019, the virus responsible for the outbreak-SARS-CoV-2-has continued to evolve. Mutations of the virus' spike protein, the main protein driving infectivity and transmissibility, are especially concerning as they may allow the virus to improve its infectivity, transmissibility, and ability to evade the immune system. Understanding how specific molecular changes can alter the behaviour of a virus is challenging for non-experts, but this information helps us to understand the pandemic we are living through and the public health measures and interventions needed to bring it under control. In response to communication challenges arising from the COVID-19 pandemic, we recently developed an online educational application to explain the molecular biology of SARS-CoV-2 spike protein mutations to the general public. We used visualisation techniques such as 3D modelling and animation, which have been shown to be highly effective teaching tools in molecular biology, allowing the viewer to better understand protein structure, function, and dynamics. We also included interactive elements for users to learn actively by engaging with the digital content, and consequently improve information retention.This chapter presents the methodological and technological framework which we used to create this resource, the 'SARS-CoV-2 Spike Protein Mutation Explorer' (SSPME). It explains how molecular visualisation and 3D modelling software were used to develop accurate models of relevant proteins; how 3D animation software was used to accurately visualise the dynamic molecular processes of SARS-CoV-2 infection, transmission, and antibody evasion; and how game development software was used to compile the 3D models and animations into a comprehensive, informative interactive application on SARS-CoV-2 spike protein mutations. This chapter indicates how cutting-edge visualisation techniques and technologies can be used to improve science communication about complex topics in molecular biology and infection biology to the general public, something that is critical to gaining control of the continuing COVID-19 pandemic.

Nanoscape, a data-driven 3D real-time interactive virtual cell environment

Our understanding of cellular and structural biology has reached unprecedented levels of detail, and computer visualisation techniques can be used to create three-dimensional (3D) representations of cells and their environment that are useful in both teaching and research. However, extracting and integrating the relevant scientific data, and then presenting them in an effective way, can pose substantial computational and aesthetic challenges. Here we report how computer artists, experts in computer graphics and cell biologists have collaborated to produce a tool called Nanoscape that allows users to explore and interact with 3D representations of cells and their environment that are both scientifically accurate and visually appealing. We believe that using Nanoscape as an immersive learning application will lead to an improved understanding of the complexities of cellular scales, densities and interactions compared with traditional learning modalities.

Concept Inventories as a Complement to Learning Progressions

Learning progressions (LPs) are descriptions of students' growing sophistication in the understanding of a particular construct through a curricular sequence. They are particularly useful for organizing complex constructs for which students do not necessarily connect concepts as taught in different courses. However, they are challenging to construct, because they attempt to linearize students' inherently nonlinear learning. As a result, it is essential to have methods to assess students' arrival at particular steps along the progression. One tool readily available to instructors is concept inventories (CIs). We have mapped published CIs to LPs for acid-base chemistry. The alignment not only provides an assessment that professors can use to pinpoint student learning, but also creates another tool to verify hypothetical LPs.  We have compared the types of questions asked on CIs in chemistry, biology, and biochemistry, as well as in some standardized test banks. The mapping of questions from CIs to steps on the LPs allows refinement of the LPs and reveals gaps in assessment tools for sophisticated concepts. This alignment is a novel addition to the cycle of validation of an LP.

Minds at Play: Using an Online Protein Folding Game, FoldIt, To Support Student Learning about Protein Folding, Structure, and the Scientific Process

Structure-function relationships of biological molecules are foundational to undergraduate biology education. In this article and supplemental information, an in-class activity is presented that uses a freely available online game to visualize the nature of chemical bonds as they relate to protein folding and structure. Activity questions and discussion guide students through a consideration of common structural elements as well as the nature of the scientific process. The activity was used in a lab section but could also work as a homework assignment. Student comments from a survey at the end of the course were overwhelmingly positive and indicated the activity helped them appreciate the complexity of protein folding as well as the scientific processes used to solve protein structures.

Identifying and Remediating Student Misconceptions in Introductory Biology via Writing-to-Learn Assignments and Peer Review

Student misconceptions are an obstacle in science, technology, engineering, and mathematics courses and unless remediated may continue causing difficulties in learning as students advance in their studies. Writing-to-learn assignments (WTL) are characterized by their ability to promote in-depth conceptual learning by allowing students to explore their understanding of a topic. This study sought to determine whether and what types of misconceptions are elicited by WTL assignments and how the process of peer review and revision leads to remediation or propagation of misconceptions. We examined four WTL assignments in an introductory biology course in which students first wrote about content by applying it to a realistic scenario, then participated in a peer-review process before revising their work. Misconceptions were identified in all four assignments, with the greatest number pertaining to protein structure and function. Additionally, in certain contexts, students used scientific terminology incorrectly. Analysis of the drafts and peer-review comments generated six profiles by which misconceptions were addressed through the peer-review process. The prevalent mode of remediation arose through directed peer-review comments followed by correction during revision. It was also observed that additional misconceptions were elicited as students revised their writing in response to general peer-review suggestions.

Creating 3D physical models to probe student understanding of macromolecular structure

The high degree of complexity of macromolecular structure is extremely difficult for students to process. Students struggle to translate the simplified two-dimensional representations commonly used in biochemistry instruction to three-dimensional aspects crucial in understanding structure-property relationships. We designed four different physical models to address student understanding of electrostatics and noncovalent interactions and their relationship to macromolecular structure. In this study, we have tested these models in classroom settings to determine if these models are effective in engaging students at an appropriate level of difficulty and focusing student attention on the principles of electrostatic attractions. This article describes how to create these unique models for four targeted areas related to macromolecular structure: protein secondary structure, protein tertiary structure, membrane protein solubility, and DNA structure. We also provide evidence that merits their use in classroom settings based on the analysis of assembled models and a behavioral assessment of students enrolled in an introductory biochemistry course. By providing students with three-dimensional models that can be physically manipulated, barriers to understanding representations of these complex structures can be lowered and the focus shifted to addressing the foundational concepts behind these properties. © 2017 by The International Union of Biochemistry and Molecular Biology, 45(6):491-500, 2017.

Practical insights on enzyme stabilization

Enzymes are efficient catalysts designed by nature to work in physiological environments of living systems. The best operational conditions to access and convert substrates at the industrial level are different from nature and normally extreme. Strategies to isolate enzymes from extremophiles can redefine new operational conditions, however not always solving all industrial requirements. The stability of enzymes is therefore a key issue on the implementation of the catalysts in industrial processes which require the use of extreme environments that can undergo enzyme instability. Strategies for enzyme stabilization have been exhaustively reviewed, however they lack a practical approach. This review intends to compile and describe the most used approaches for enzyme stabilization highlighting case studies in a practical point of view.

Using Pre-Assessment and In-Class Questions to Change Student Understanding of Molecular Movements

Understanding how different types of molecules move through cell membranes is a fundamental part of cell biology. To identify and address student misconceptions surrounding molecular movement through cell membranes, we surveyed student understanding on this topic using pre-class questions, in-class clicker questions, and subsequent exam questions in a large introductory biology course. Common misconceptions identified in student responses to the pre-class assessment questions were used to generate distractors for clicker questions. Two-tier diagnostic clicker questions were used to probe incoming common student misconceptions (first tier) and their reasoning (second tier). Two subsequent lectures with assessment clicker questions were used to help students construct a new framework to understand molecular movement through cell membranes. Comparison of pre-assessment and post-assessment (exam) performance showed dramatic improvement in students' understanding of molecular movement: student answers to exam questions were 74.6% correct with correct reasoning while only 1.3% of the student answers were correct with correct reasoning on the pre-class assessment. Our results show that students' conceptual understanding of molecular movement through cell membranes progressively increases through discussions of a series of clicker questions and suggest that this clicker-based teaching strategy was highly effective in correcting common student misconceptions on this topic.

Computational library design for increasing haloalkane dehalogenase stability

We explored the use of a computational design framework for the stabilization of the haloalkane dehalogenase LinB. Energy calculations, disulfide bond design, molecular dynamics simulations, and rational inspection of mutant structures predicted many stabilizing mutations. Screening of these in small mutant libraries led to the discovery of seventeen point mutations and one disulfide bond that enhanced thermostability. Mutations located in or contacting flexible regions of the protein had a larger stabilizing effect than mutations outside such regions. The combined introduction of twelve stabilizing mutations resulted in a LinB mutant with a 23 °C increase in apparent melting temperature (Tm,app , 72.5 °C) and an over 200-fold longer half-life at 60 °C. The most stable LinB variants also displayed increased compatibility with co-solvents, thus allowing substrate conversion and kinetic resolution at much higher concentrations than with the wild-type enzyme.

Visualizing protein interactions and dynamics: evolving a visual language for molecular animation

Undergraduate biology education provides students with a number of learning challenges. Subject areas that are particularly difficult to understand include protein conformational change and stability, diffusion and random molecular motion, and molecular crowding. In this study, we examined the relative effectiveness of three-dimensional visualization techniques for learning about protein conformation and molecular motion in association with a ligand-receptor binding event. Increasingly complex versions of the same binding event were depicted in each of four animated treatments. Students (n = 131) were recruited from the undergraduate biology program at University of Toronto, Mississauga. Visualization media were developed in the Center for Molecular and Cellular Dynamics at Harvard Medical School. Stem cell factor ligand and cKit receptor tyrosine kinase were used as a classical example of a ligand-induced receptor dimerization and activation event. Each group completed a pretest, viewed one of four variants of the animation, and completed a posttest and, at 2 wk following the assessment, a delayed posttest. Overall, the most complex animation was the most effective at fostering students' understanding of the events depicted. These results suggest that, in select learning contexts, increasingly complex representations may be more desirable for conveying the dynamic nature of cell binding events.