Mikhail Ivan, Yildirim Håkan H, Lindahl Emma C H, Schweda Elke K H
Clinical Research Centre, Karolinska Institutet and University College of South Stockholm, NOVUM, S-141 86 Huddinge, Sweden.
Anal Biochem. 2005 May 15;340(2):303-16. doi: 10.1016/j.ab.2005.02.020.
Lipid A isolated by mild acid hydrolysis from lipopolysaccharides of 22 nontypeable and 2 type f Haemophilus influenzae strains was investigated using electrospray ionization coupled to quadrupole ion trap mass spectrometry. The lengths, positions, and number of acyl chains in the lipid A molecule were determined using multiple-step tandem mass spectrometry (MSn). All of the analyzed strains showed a major lipid A molecule comprising beta-2-amino-2-deoxy-D-glucopyranose-(1-->6)-alpha-2-amino-2-deoxy-D-glucopyranose phosphorylated at the C4' and C1 positions. The C2/C2' and C3/C3' positions were substituted by amide-linked and ester-linked 3-hydroxytetradecanoic acid chains, respectively. The fatty acid chains on C3' and C2' were further esterified by tetradecanoic acid chains. In all strains, minor amounts of lipid A molecules with different acylation patterns were identified. Thus, structures comprising the hexaacylated lipid A with the C2 or C3 position being substituted by 3-hydroxydecanoic acid, and hexaacylated lipid A with the C3 and C3' positions being substituted by 3-hydroxydodecanoic or dodecanoyloxytetradecanoic acid, respectively, were found. In addition, lipid A with an acetyl group attached to the 3-hydroxytetradecanoic acid groups attached to the C2 or C3 position was detected in two nontypeable H. influenzae strains.
采用电喷雾电离与四极杆离子阱质谱联用技术，对从22株不可分型和2株f型流感嗜血杆菌脂多糖中通过温和酸水解分离得到的脂质A进行了研究。利用多步串联质谱法（MSn）确定了脂质A分子中酰基链的长度、位置和数量。所有分析菌株均显示出一种主要的脂质A分子，其由在C4'和C1位置磷酸化的β-2-氨基-2-脱氧-D-吡喃葡萄糖-(1→6)-α-2-氨基-2-脱氧-D-吡喃葡萄糖组成。C2/C2'和C3/C3'位置分别被酰胺连接和酯连接的3-羟基十四烷酸链取代。C3'和C2'上的脂肪酸链进一步被十四烷酸链酯化。在所有菌株中，均鉴定出少量具有不同酰化模式的脂质A分子。因此，发现了包含C2或C3位置被3-羟基癸酸取代的六酰化脂质A，以及C3和C3'位置分别被3-羟基十二烷酸或十二烷酰氧基十四烷酸取代的六酰化脂质A的结构。此外，在两株不可分型流感嗜血杆菌菌株中检测到了在连接到C2或C3位置的3-羟基十四烷酸基团上连接有乙酰基的脂质A。
