Using a Community-Based Participatory Mixed Methods Research Approach to Develop, Evaluate, and Refine a Nutrition Intervention to Replace Sugary Drinks with Filtered Tap Water among Predominantly Central-American Immigrant Families with Infants and Toddlers: The Water Up @Home Pilot Evaluation Study.

Descriptions of the implementation of community-based participatory mixed-methods research (CBPMMR) in all phases of the engagement approach are limited. This manuscript describes the explicit integration of mixed-methods in four stages of CBPR: (1) connecting and diagnosing, (2) prescribing-implementing, (3) evaluating, and (4) disseminating and refining an intervention that aimed to motivate Latino parents (predominantly Central American in the US) of infants and toddlers to replace sugary drinks with filtered tap water. CBPMMR allowed for co-learning that led to the identification of preliminary behavioral outcomes, insights into potential mechanisms of behavior change, and revisions to the intervention design, implementation and evaluation.

ß-Hairpin Crowding Agents Affect α-Helix Stability in Crowded Environments.

The dense, heterogeneous cellular environment is known to affect protein stability. It is now recognized that attractive "quinary" interactions with other biomacromolecules in the cell, referred to as the crowding agents, play a significant role in determining the stability of the protein of interest or test protein. These attractive interactions can reduce or overcome the stabilizing effect of the excluded volume of the crowding agents. However, the roles of specific interactions, such as hydrogen bonding and side chain-side chain hydrophobic interactions, are still unclear. Here, we use molecular simulation to investigate the roles played by hydrophobic interactions and hydrogen bonding between a small helical test protein and equally sized crowding agent proteins in a fixed ß-hairpin configuration. The test protein and crowding agents are represented by a coarse-grained protein model, and we use multicanonical molecular dynamics to study the folding thermodynamics of the test protein. Our results confirm that the stability of the test protein depends on the hydrophobicity of the crowding agents and that the stability of the test protein is reduced through favorable side chain-side chain interactions that preferentially stabilize the unfolded states. In addition, we show that when the intermolecular hydrophobic interactions are more favorable than the intramolecular hydrophobic interactions, the ß-rich crowding agents can completely destabilize the test protein, causing it to adopt configurations with increased ß-content and preventing it from forming its native helical state. Similarities between our results and those seen in the formation of amyloid fibrils are also discussed.

Protein-protein interactions affect alpha helix stability in crowded environments.

The dense, heterogeneous cellular environment is known to affect protein stability through interactions with other biomacromolecules. The effect of excluded volume due to these biomolecules, also known as crowding agents, on a protein of interest, or test protein, has long been known to increase the stability of a test protein. Recently, it has been recognized that attractive protein-crowder interactions play an important role. These interactions affect protein stability and can destabilize the test protein. However, most computational work investigating the role of attractive interactions has used spherical crowding agents and has neglected the specific roles of crowding agent hydrophobicity and hydrogen bonding. Here we use multicanonical molecular dynamics and a coarse-grained protein model to study the folding thermodynamics of a small helical test protein in the presence of crowding agents that are themselves proteins. Our results show that the stability of the test protein depends on the hydrophobicity of the crowding agents. For low values of crowding agent hydrophobicity, the excluded volume effect is dominant, and the test protein is stabilized relative to the dilute solution. For intermediate values of the crowding agent hydrophobicity, the test protein is destabilized by favorable side chain-side chain interactions stabilizing the unfolded states. For high values of the crowding agent hydrophobicity, the native state is stabilized by the strong intermolecular attractions, causing the formation of a packed structure that increases the stability of the test protein through favorable side chain-side chain interactions. In addition, increasing crowding agent hydrophobicity increases the "foldability" of the test protein and alters the potential energy landscape by simultaneously deepening the basins corresponding to the folded and unfolded states and increasing the energy barrier between them.