Pašalić Lea, Jakas Andreja, Pem Barbara, Bakarić Danijela
Division of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, Bijenička Cesta 54, 10000 Zagreb, Croatia.
Antibiotics (Basel). 2023 Jul 21;12(7):1216. doi: 10.3390/antibiotics12071216.
Cell-penetrating peptides (CPPs) are short peptides built up from dominantly cationic and hydrophobic amino acid residues with a distinguished ability to pass through the cell membrane. Due to the possibility of linking and delivering the appropriate cargo at the desired location, CPPs are considered an economic and less invasive alternative to antibiotics. Besides knowing that their membrane passage mechanism is a complex function of CPP chemical composition, the ionic strength of the solution, and the membrane composition, all other details on how they penetrate cell membranes are rather vague. The aim of this study is to elucidate the ad(de)sorption of arginine-/lysine- and phenylalanine-rich peptides on a lipid membrane composed of 1,2-dipalmitoyl--glycero-3-phosphocholine (DPPC) lipids. DSC and temperature-dependent UV-Vis measurements confirmed the impact of the adsorbed peptides on thermotropic properties of DPPC, but in an inconclusive way. On the other hand, FTIR spectra acquired at 30 °C and 50 °C (when DPPC lipids are found in the gel and fluid phase, respectively) unambiguously confirmed the proton transfer between particular titratable functional groups of R5F2/K5F2 that highly depend on their immediate surroundings (DPPC or a phosphate buffer). Molecular dynamic simulations showed that both peptides may adsorb onto the bilayer, but K5F2 desorbs more easily and favors the solvent, while R5F2 remains attached. The results obtained in this work highlight the importance of proton transfer in the design of CPPs with their desired cargo, as its charge and composition dictates the possibility of entering the cell.
细胞穿透肽（CPPs）是由主要为阳离子和疏水氨基酸残基组成的短肽，具有穿过细胞膜的独特能力。由于能够在所需位置连接并递送合适的货物，CPPs被认为是一种经济且侵入性较小的抗生素替代品。除了知道它们的膜通道机制是CPP化学成分、溶液离子强度和膜成分的复杂函数外，关于它们如何穿透细胞膜的所有其他细节都相当模糊。本研究的目的是阐明富含精氨酸/赖氨酸和苯丙氨酸的肽在由1,2-二棕榈酰-sn-甘油-3-磷酸胆碱（DPPC）脂质组成的脂质膜上的吸附/解吸附情况。差示扫描量热法（DSC）和温度依赖性紫外可见光谱测量证实了吸附肽对DPPC热致性质的影响，但结果并不确定。另一方面，在30℃和50℃（分别为DPPC脂质处于凝胶相和流体相时）获得的傅里叶变换红外光谱（FTIR）明确证实了R5F2/K5F2特定可滴定官能团之间的质子转移，这高度依赖于它们的直接环境（DPPC或磷酸盐缓冲液）。分子动力学模拟表明，两种肽都可能吸附到双层膜上，但K5F2更容易解吸附并偏向溶剂，而R5F2则保持附着。这项工作获得的结果突出了质子转移在设计携带所需货物的CPPs中的重要性，因为其电荷和组成决定了进入细胞的可能性。
