Taylor T Matthew, Davidson P Michael, Bruce Barry D, Weiss Jochen
Department of Food Science and Technology, The University of Tennessee, 2605 River Road, Knoxville, TN 37996-4591, USA.
J Agric Food Chem. 2005 Nov 2;53(22):8722-8. doi: 10.1021/jf050726k.
The thermal stability of phosphatidylcholine (PC) liposomes (colloidal dispersions of bilayer-forming polar lipids in aqueous solvents) in the presence and absence of the antimicrobial polypeptide nisin was evaluated using differential scanning calorimetry (DSC) and low-intensity ultrasonic spectroscopy (US). PC liposome mixtures with varying acyl chain lengths (C16:0 and C18:0) were formed in buffer with or without entrapped nisin. Gel-to-liquid crystalline phase transition temperatures (T(M)) of liposomes determined from DSC thermograms were in excellent agreement with those determined by ultrasonic velocity and attenuation coefficient measurements recorded at 5 MHz. The dipalmitoylphosphatidylcholine (DPPC) T(M) measured by DSC was approximately 41.3 and approximately 40.7 degrees C when measured by ultrasonic spectroscopy. The T(M) of distearoylphosphatidylcholine (DSPC) and DPPC/DSPC 1:1 liposomes was 54.3 and 54.9 degrees C and approximately 44.8 and approximately 47.3 degrees C when measured by DSC and US, respectively. The thermotropic stability generally increased upon addition of nisin. Analysis of the stepwise decrease in ultrasonic velocity with temperature indicated an increased compressibility corresponding to a loss of structure upon heating.
利用差示扫描量热法（DSC）和低强度超声光谱法（US），评估了在存在和不存在抗菌多肽乳链菌肽的情况下，磷脂酰胆碱（PC）脂质体（双层形成极性脂质在水性溶剂中的胶体分散体）的热稳定性。在含有或不含包封乳链菌肽的缓冲液中形成了具有不同酰基链长度（C16:0和C18:0）的PC脂质体混合物。从DSC热谱图确定的脂质体的凝胶-液晶相转变温度（T(M)）与通过在5MHz下记录的超声速度和衰减系数测量确定的温度非常一致。通过DSC测量的二棕榈酰磷脂酰胆碱（DPPC）的T(M)约为41.3℃，通过超声光谱法测量时约为40.7℃。通过DSC和US测量时，二硬脂酰磷脂酰胆碱（DSPC）和DPPC/DSPC 1:1脂质体的T(M)分别为54.3和54.9℃以及约44.8和约47.3℃。添加乳链菌肽后，热致稳定性通常会增加。对超声速度随温度的逐步降低进行分析表明，随着加热结构丧失，压缩性增加。
