在分子生物学和药理学领域，小分子是一种低分子量(< 900道尔顿)的有机化合物，可以调节生物过程，大小约为1nm。大多数药物都是小分子的。较大的结构，如核酸和蛋白质，以及许多多糖不是小分子，尽管它们的组成单体(分别为核糖核苷酸或脱氧核糖核苷酸、氨基酸和单糖)通常被认为是小分子。小分子可以作为探索生物功能的研究工具，也可以作为开发新型治疗剂的先导。有些可以抑制蛋白质的特定功能或破坏蛋白质之间的相互作用。
药理学通常将“小分子”一词限制为与特定生物大分子结合并作为效应剂，改变靶标活性或功能的分子。小分子可以有各种各样的生物学功能或应用，作为细胞信号分子，药物在医学，农药在农业，以及在许多其他角色。这些化合物可以是天然的(如次级代谢产物)或人工的(如抗病毒药物);它们可能对疾病有有益的作用(如药物)，也可能有害(如致畸物和致癌物)。
Cosmo Bio抗体,Anti Plumbagin mAb (Clone 3A3),CAC-KYU-HT-M005
Application: ELISA
Clonality: Monoclonal
Host: Mouse
Purification: Ig-PG
Within the fields of molecular biology and pharmacology, a small molecule is a low molecular weight (< 900 daltons) organic compound that may regulate a biological process, with a size on the order of 1 nm. Most drugs are small molecules. Larger structures such as nucleic acids and proteins, and many polysaccharides are not small molecules, although their constituent monomers (ribo- or deoxyribonucleotides, amino acids, and monosaccharides, respectively) are often considered small molecules. Small molecules may be used as research tools to probe biological function as well as leads in the development of new therapeutic agents. Some can inhibit a specific function of a protein or disrupt protein–protein interactions.
Pharmacology usually restricts the term “small molecule” to molecules that bind specific biological macromolecules and act as an effector, altering the activity or function of the target. Small molecules can have a variety of biological functions or applications, serving as cell signaling molecules, drugs in medicine, pesticides in farming, and in many other roles. These compounds can be natural (such as secondary metabolites) or artificial (such as antiviral drugs); they may have a beneficial effect against a disease (such as drugs) or may be detrimental (such as teratogens and carcinogens).