球狀蛋白，是一種廣泛應用於科學上且扮演著關鍵作用的蛋白質。緩衝溶液常為球狀蛋白質之溶劑，但卻未曾有人探討緩衝溶液對球狀蛋白質吸附行為之影響。本論文擬探討牛血清白蛋白(Bovine Serum Albumin, BSA)於磷酸鹽緩衝溶液中之吸附行為。
本研究使用影像數位化懸掛氣泡測量儀，量測牛血清蛋白於磷酸鹽緩衝溶液(0 - 44 mM)中吸附至乾淨氣-液界面之動態表面張力。於BSA吸附後期，表面張力保持近乎恆定達數小時，此為其平衡表面張力。BSA在0.2–15 (10-10 mol/cm3)濃度範圍內於0、10、44mM磷酸鹽緩衝溶液中，其平衡張力維持在52.20.6、54.10.2與53.90.1 mN/m。
本研究亦量測BSA於磷酸鹽緩衝溶液(0-44mM)中之動態張力。當BSA濃度為6.0  10-10 mol/cm3，改變緩衝溶液濃度(0-300M)，緩衝溶液濃度越高時，張力下降趨勢趨緩；但當緩衝溶液濃度大於300M後，張力下降趨勢則改為變快。在BSA濃度為2和15 (10-10 mol/cm3)時，動態張力下降趨勢亦呈相同行為。
BSA於磷酸鹽緩衝溶液中之吸附過程，系統檢測到諸多微小的界面擾動。藉由分析這些擾動所引起的張力和表面積之變化，可用來計算表面擴張速率[d(lnA)/dt]和表面張力變化速率(d/dt)，隨後得到膨脹模量[(E = (d/dt)/(dlnA/dt)]。隨著緩衝溶液濃度升高(300M至1mM)，膨脹模量變化趨勢些微升高；隨著BSA濃度升高(2至610-10 mol/cm3)，膨脹模量變化趨勢亦呈相同行為，但當BSA濃度升高至1510-10 mol/cm3，膨脹模量變化趨勢升高更加明顯。

Globular proteins, characterized by a nearly spherical three-dimensional conformation, are extensively utilized in numerous industrial and scientific applications; wherein, they are predominantly utilized in conjunction with aqueous buffer as solvents. However, to date, the influence of buffer on the surface-active nature and interfacial rheological behavior of globular proteins is yet to be ascertained. This study aims to investigate the effect of phosphate buffer on the surface activity and dilational rheology of globular protein Bovine Serum Albumin (BSA).
The relaxations of surface tension (ST) and surface area (SA), resulting from the adsorption of BSA molecules onto the clean air-water interface, were measured by a pendant bubble tensiometer. The relaxation data revealed that during the latter stages of the BSA’s adsorption process, the ST kept fairly constant for several hours. Consequently, these fairly constant ST values were set as the equilibrium ST. For BSA(aq) in 0, 10 and 44 mM phosphate buffer, the equilibrium ST remained essentially unchanged at 52.20.6, 54.10.2 and 53.90.1 mN/m, respectively, over a wide concentration range [CBSA = 0.2 – 15.0 (10-10 mol/cm3)].
The effect of buffer concentration [Cbuffer = 0 – 44 mM] on the dynamic ST of BSA was examined as well. The data revealed that at a fixed protein concentration (e.g., CBSA = 6.010-10 mol/cm3), an increase in buffer concentration (from 0 – 300 M) resulted in an increasingly slower ST relaxation. However, with a further increase in buffer concentration (Cbuffer > 300 M), the ST relaxed progressively faster. A similar behavior was also observed at a more elevated and dilute BSA concentration [i.e., CBSA = 2.0 and 15.0 (10-10 mol/cm3)].
Numerous minute interfacial perturbances (induced by small ambient temperature variations) were also detected amidst the SA and ST relaxations. The surface dilational rate (dlnA/dt) and rate of ST change (d/dt) of these distinct perturbances were estimated and then after, the dilational modulus of the adsorbed BSA film [E = (d/dt)/(dlnA/dt)] was evaluated. The results revealed that an increase in buffer concentration (from 300 M – 1mM) corresponded to a slight increase in the dilational modulus of the adsorbed BSA film; likely indicating a change in the rigidity of the adsorbed film at an elevated buffer concentration.

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