# The Role of Secondary Interactions Relevant to Biological Reductions of Small Molecules

> **NIH NIH R35** · UNIVERSITY OF MICHIGAN AT ANN ARBOR · 2022 · $373,731

## Abstract

Abstract:
The conversion of dinitrogen to ammonia is required for the global nitrogen cycle and is accomplished biologically
by nitrogenase enzymes. Although highly inert, dinitrogen is “fixed” by nitrogenase enzymes, and made
biologically available, allowing uptake to form key nutrients necessary to sustain life. The nitrogenase enzyme
active site features a multi-metallic core contained within a complex network of amino acids, which are necessary
to orchestrate a series of multi-proton, multi-electron transfers to small molecule substrates during the reduction
process. Although crucial for dinitrogen reduction, the precise molecular role that these secondary interactions
serve to promote reduction is not well known. More explicitly, the scientific community does not precisely know
where and how substrates bind, how electrons are delivered, and products released. Thus, there is an inherent
gap in our knowledge underlying key contributors to nitrogenase reactivity. To address this gap, this proposal
targets the design and study of small molecular constructs that contain highly directed and variable secondary
coordination sphere interactions. We will use a rational design approach to prepare synthetic analogues that
feature modifiable appended functionality (hydrogen-bond donors, Lewis acids/bases) in the secondary
coordination sphere environment to evaluate cooperative reactivity. We will use these molecular structures to
test key mechanistic hypotheses regarding the molecular-level reduction of substrates using secondary-sphere
cooperativity. We propose that the same type of interactions evaluated in our synthetic systems that promote
nitrogenase-type activity can be, by extension, adapted to describe biological systems. The knowledge we
acquire will provide key needed contributions to mechanistic studies of nitrogenase function and also synthetic
nitrogenases. Substrate activation promoted by highly directed secondary sphere interactions is a broad theme
among many biocatalytic cycles, and thus, we envision that the results of our studies will have broad utility to
elucidate meaningful contributors to enzymatic reactivity.

## Key facts

- **NIH application ID:** 10451600
- **Project number:** 5R35GM136360-03
- **Recipient organization:** UNIVERSITY OF MICHIGAN AT ANN ARBOR
- **Principal Investigator:** Nathaniel Kolnik Szymczak
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $373,731
- **Award type:** 5
- **Project period:** 2020-09-01 → 2025-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10451600

## Citation

> US National Institutes of Health, RePORTER application 10451600, The Role of Secondary Interactions Relevant to Biological Reductions of Small Molecules (5R35GM136360-03). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10451600. Licensed CC0.

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