基质辅助激光解吸电离Matrix-assisted laser desorption/ionization

常用紫外激光（337 nm 氮激光或 355 nm Nd:YAG 激光），常用基质有 α-氰基-4-羟基肉桂酸（CHCA，用于肽）、芥子酸（SA，用于蛋白质）和 2,5-二羟基苯甲酸（DHB，用于糖和小分子）。基质隔离样品分子并吸收激光能量，避免样品直接受热分解。MALDI 主要产生单电荷离子 [M+H]⁺，谱图简单。TOF 分析器根据离子在无场飞行管中的飞行时间（t ∝ √(m/z)）测定质量，理论上没有质量上限，可测数十万道尔顿的分子。

UV lasers are common (337 nm nitrogen or 355 nm Nd:YAG), with matrices such as α-cyano-4-hydroxycinnamic acid (CHCA, for peptides), sinapinic acid (SA, for proteins) and 2,5-dihydroxybenzoic acid (DHB, for sugars and small molecules). The matrix isolates sample molecules and absorbs the laser energy, sparing them direct heating and decomposition. MALDI gives mostly singly charged [M+H]⁺ ions and simple spectra. The TOF analyser measures mass from flight time through a field-free tube (t ∝ √(m/z)) and has in principle no upper mass limit, reaching hundreds of thousands of daltons.

1985 年德国明斯特大学的卡拉斯和希伦坎普提出基质辅助激光解吸的概念。1987 年日本岛津公司的工程师田中耕一用超细钴粉悬浮在甘油中作基质，首次实现了分子量达 34 000 的蛋白质的软激光解吸电离，他因此获 2002 年诺贝尔化学奖——田中耕一当时只有学士学位，是罕见的企业工程师获奖者。1988 年卡拉斯和希伦坎普用有机小分子基质实现了更实用的 MALDI。

In 1985 Karas and Hillenkamp at the University of Münster proposed matrix-assisted laser desorption. In 1987 Koichi Tanaka, an engineer at Shimadzu in Japan, used ultrafine cobalt powder in glycerol as a matrix to achieve the first soft laser desorption ionisation of proteins up to 34,000 Da, for which he shared the 2002 Nobel Prize in Chemistry; with only a bachelor's degree, he was a rare industrial engineer laureate. In 1988 Karas and Hillenkamp achieved more practical MALDI with small organic matrices.

MALDI-TOF 用于蛋白质和多肽分子量测定、肽质量指纹谱鉴定蛋白质、合成高分子分子量分布分析、寡核苷酸质量检验；临床微生物实验室用 MALDI-TOF 根据细菌核糖体蛋白指纹在几分钟内鉴定菌种，取代了传统的生化鉴定；MALDI 质谱成像可在组织切片上直接绘制药物、脂质和代谢物的空间分布。

MALDI-TOF measures molecular weights of proteins and peptides, identifies proteins by peptide mass fingerprinting, analyses molecular-weight distributions of synthetic polymers and checks oligonucleotides; clinical microbiology laboratories identify bacteria within minutes from fingerprints of their ribosomal proteins, replacing biochemical tests; and MALDI imaging maps drugs, lipids and metabolites directly on tissue sections.