Spermine: A Hemoglobin Modifier That Reduces Autoxidation and Regulates Oxygen Delivery.

Area of Science:

• Biochemistry
• Biophysics
• Materials Science

Background:

• Autoxidation of hemoglobin to methemoglobin (MetHb) hinders the development of hemoglobin-based oxygen carriers (HBOCs).
• Understanding how molecules like spermine affect hemoglobin stability and function is crucial for HBOC research.

Purpose of the Study:

• To investigate the effects of spermine on adult hemoglobin (HbA) stability, aggregation, structure, and oxygen-carrying function.
• To explore spermine's potential in mitigating HbA autoxidation and enhancing its oxygen affinity for HBOC applications.

Main Methods:

• Dynamic light scattering, static light scattering, colloid osmotic pressure, and thermal denaturation assays were used to assess HbA stability and aggregation.
• UV-vis spectroscopy, MetHb formation assays, and hydroxyl radical scavenging determined spermine's antioxidant capacity.
• Oxygen dissociation assays, surface plasmon resonance, microfluidic modulation spectroscopy, molecular docking, and molecular dynamics simulations elucidated spermine's effects on HbA's structure, oxygen affinity, and binding interactions.

Main Results:

• Spermine was found to enhance HbA's oxygen affinity, indicated by changes in the P50 value.
• Spermine demonstrated antioxidant capacity by reducing MetHb formation and scavenging hydroxyl radicals.
• Spermine induced a conformational shift in HbA towards the 'R' state, transforming partial α-helices to β-sheets and binding to specific residues (βASP99, βGLU101, αTHR38, αASN97).

Conclusions:

• Spermine effectively enhances HbA's oxygen affinity and significantly reduces its autoxidation.
• Spermine shows considerable promise for applications in hemoglobin-based oxygen carriers and hemoglobin modification research.