Actin is one of the most abundant proteins in eukaryotic cells and is a key component of the cytoskeleton, the internal framework of the cell. Its most remarkable characteristic is its dynamic nature—it can rapidly assemble and disassemble, thereby driving cell movement and changes in cell shape.

The transforming growth factor-β (TGF-β) superfamily comprises over 30 members, including TGF-β, Activin, Inhibin, bone morphogenetic proteins (BMPs), and growth differentiation factors (GDFs). It can be roughly divided into two subfamilies: the TGF-β/Activin/Nodal subfamily and the BMP/GDF/MIS (Müllerian inhibiting substrate) subfamily.

The growth hormone (GH) family comprises pituitary GH, placental lactogens (PLs), and prolactin (PRL)—evolutionarily related hormones that signal through single-pass, class-I cytokine receptors coupled to JAK2-STAT, MAPK, and PI3K cascades.

The first discovery of fetuin-A dates back to 1944 by K. Pedersen in the blood of a fetal calf (hence the name “fetuin”) . Many years later, the independent studies by J.F. Heremans and K. Schmid with W. Burgi in 1960 and 1961, respectively, purified fetuin-A in humans, and hence it is now also known as α2-Heremans-Schmid glycoprotein (AHSG) in recognition of the discoverers.

Transferrin (TRF) is an important glycoprotein in human plasma, mainly synthesized in the liver. It is composed of 679 amino acid residues, with glycose accounting for about 6%. It has two highly homologous domains, the N - terminal and C - terminal. Each domain has a Fe³⁺ binding site and can reversibly bind two Fe³⁺.

Acetyl-Histone H3/H4 In eukaryotic nuclei, ~150 bp of DNA is wrapped around the histone octamer, which consists of two copies of four core histones (i.e., H2A, H2B, H3, and H4) to form a nucleosome, the fundamental unit of chromatin. Post-translational modifications on these histones play a critical role in genome function, including the regulation of transcription and the maintenance of genome integrity [1]. Since H3 and H4 are more stably integrated into nucleosomes compared to H2A and H2B , the modifications on H3 and H4 can act as long-term memory of epigenetic regulation[2].

High background No signal Too much signal - whole plate turned uniformly blue Standard curve achieved but poor discrimination between points Poor duplicates Poor assay to assay reproducibility No signal when a signal is expected, but standard curve looks fine Samples are reading too high, but standard curve looks fine Very Low Readings Across the Plate Green color develops upon addition of stop solution when using streptavidin-HRP Edge Effects

Depending on the detection purpose, common types of ELISA include the indirect method (for measuring antibodies), the double antibody sandwich method (for measuring antigens), and competitive methods. Among these, the double antibody sandwich method and the indirect method are the most widely used. The following example will detail the standard operating procedures and key considerations for the double antibody sandwich method.

The tumor necrosis factor superfamily (TNFSF) is a group of proteins that play a wide and important role in biology. Currently, 19 ligands have been identified in this family, such as TNF-α, TNF-β, CD40L, FasL, TRAIL, RANKL, etc., and 29 receptors correspond to them.

The ELISA sample collection and storage conditions listed below are intended as general guidelines. Specific protocols may vary by cell line or tissue type. If storing sample for extended length of time, testing sample stability is recommended. Avoid repeated freeze-thaw cycles for all sample types.