Oxygenbinding

Oxygen binding refers to the reversible association of molecular oxygen (O2) with a binding partner, typically a protein or a metal center in a coordination complex. In biological systems, oxygen binding underpins respiration and cellular metabolism, while in chemistry it relates to the study of coordination compounds and catalysis.

In animals, the principal oxygen-binding proteins are hemoglobin and myoglobin. Hemoglobin is a tetrameric protein in red blood cells that binds O2 at the heme iron and exhibits cooperative binding, producing a sigmoidal oxygen dissociation curve. Myoglobin is a monomeric heme protein in muscle that binds O2 with higher affinity to facilitate storage and diffusion.

Factors modulating hemoglobin's affinity include partial pressure of O2, pH (Bohr effect), temperature, and allosteric effectors such as 2,3-bisphosphoglycerate. In lungs, high pO2 promotes binding; in tissues, lower pO2 and higher CO2 promote release.

Other oxygen-binding systems include hemocyanin in some invertebrates, which uses copper to bind O2, and various oxidases or oxygen-transport proteins. Binding strength is often described by dissociation constants (Kd) or P50 values, and sometimes by the Hill coefficient to indicate cooperativity. Kinetic parameters (on-rate and off-rate) determine how rapidly binding and release occur.

Applications include the study of hypoxia, design of artificial oxygen carriers, and understanding oxygen transport in physiology and biochemistry.