This study investigated the effects of nitric oxide donors, ATP, sodium, and potassium ions on the unfolding and aggregation of hemoglobin. The researchers found that nitric oxide decreased hemoglobin's unfolding temperature, while ATP increased the unfolding temperature, regardless of whether sodium or potassium buffer was used. However, the combined effects of ATP and nitric oxide depended strongly on the buffer ion composition. Additionally, potassium facilitated partial unfolding of hemoglobin's alpha-helical structures even at room temperature. The results provide insight into how small molecules can regulate protein activity through effects on structure.

1. Effects of Salts, Nitric Oxide Donors and ATP on
Hemoglobin Unfolding and Aggregation
Rasha Bassam1, 2, Christina Kordewiner1, Dariusz Porst1, Aysegül Temiz Artmann1, Gerhard M.
Artmann1, Peter Kayser1, Jürgen Hescheler 2, Ilya Digel1
1 Institute for Bioengineering, FH Aachen University of Applied Sciences, D-52428 Jülich
2 Institute of Neurophysiology, University of Cologne, Robert-Koch-Str. 39, 50931 Cologne
bassam@fh-aachen.de
Fig .1: Effect of different small solutes in (a) Na-buffer with (b) NO (c) ATP
and (d) NO-ATP. Additionally effect of small solutes in (e) K-buffer with (f)
NO (g) ATP and (h) NO-ATP respectively
Fig .3: Influence of ATP and spermine NONOate on unfolding of Hb samples prepared in Na- and K-buffer
Fig .2: Schematics of protein dynamics interactions
Background
• Protein activity regulation by small molecules provides a rapid and flexible tool of metabolic control and is known to be a
key event in cellular signaling pathways.
• Effects of small solutes on protein behavior can be studied for instance by examining changes of protein secondary
structure or as well of protein thermal aggregation.
• This study aimed at investigating aspects of the impact of the nitric oxide donor spermine NONOate, of adenosine-5'-
triphosphate (ATP) and of sodium/potassium ions on the dynamics of thermal unfolding and aggregation of normal human
hemoglobin (Hb).
Outlook
• Irrespectively of the Na+/K+-environment, Hb’s unfolding temperature was persistently decreased by spermine NONOate
and systematically increased by ATP.
• Mutual effects of ATP and NO were strongly influenced by particular buffer ionic compositions.
• Presence of potassium facilitated a partial unfolding of Hb alpha-helical structures even at room temperature.
• The obtained data might shed more light on molecular mechanisms involved in the regulation of protein activity by small
solutes.
Protein
Dynamics
Adenosine
Triphosphate
(ATP)
2, 3-
Diphosphoglycerate
(2, 3-DPG)
Sodium
(Na+)
Potassium
(K+)
Nitric Oxide
(NO)
Carbon Dioxide
(CO2)
Aggregation
TemperatureUnfolding
Temperature
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