# Revealing the Impact of pH on Lipase Structure and Surface Propensity at the Air–Water Interface and in Aqueous Aerosols

## TL;DR

This study explores how pH affects the structure and behavior of a marine enzyme at air-water interfaces and in sea spray aerosols.

## Contribution

The study reveals pH-dependent structural changes and surface activity of Burkholderia cepacia lipase in marine aerosols.

## Key findings

- BCL shows increased surface propensity at higher pH compared to acidic conditions.
- Molecular dynamics simulations reveal structural changes in BCL at acidic interfaces.
- BCL aerosol particles react heterogeneously with gaseous nitric acid.

## Abstract

Sea spray aerosols (SSAs), generated through oceanic
bubble bursting,
are chemically complex particles that significantly influence climate
processes and ecosystem health. These aerosols are enriched with biological
macromolecules such as enzymes and proteins, whose structure and activity
at the air–water interface remain poorly understood, particularly
under the highly variable pH conditions of SSAs. In this study, we
investigate the pH-dependent surface activity of Burkholderia
cepacia lipase (BCL), a model extracellular enzyme commonly
found in marine environments. Using surface tension and infrared reflection–absorption
spectroscopy (IRRAS) measurements, we observe that BCL exhibits increased
surface propensity at higher pH compared to acidic conditions. All-atom
molecular dynamics simulations further reveal molecular-level insight
into these observations, showing structural changes in BCL at the
interface in acidic environments with new, highly atmosphere exposed
conformations. Additionally, we explore the heterogeneous reactivity
of BCL-containing aerosol particles with gaseous nitric acid to identify
potential reactive sites relevant to interactions with atmospheric
trace gases. Understanding these heterogeneous reaction pathways of
biological macromolecules not only may be relevant for SSAs but also
has broad implications for the atmospheric reactivity of bioaerosols.