As the size and complexity of 3D models increase, the need for scaffolds becomes more and more obvious. In addition to space control, cell aggregates also need to exchange nutrients and gases. When the aggregate thickness is 1-2 mm, the problem of cell death will occur due to lack of mass transfer, mainly through the exchange of nutrients and waste metabolites. This has been solved through the use of highly porous scaffolds, where the basic design considers shape, cell adhesion sites and the flow of gases, nutrients, and metabolites. Scaffolds can be made from either natural or synthetic materials. Many 3D culture systems are already available. Biomaterials can be used in 3D cell culture to enhance various forms of culture efficiency and cell function, including hydrogel, solid scaffold, acellular natural tissue and ultra-low attachment (ULA) surface.

Signaling pathways link extracellular cues to cellular responses, so that cells are able to adapt to the changes in the environment. The signals are processed as a series of molecular events in cells. Proteins responsible for detecting the signal are termed receptors or sensors, which are the first nodes in signaling transduction pathways. <br> <br>How the receptors receive the signals and initiate the signaling transduction processes is under intensive research, especially ACE2, the entry point for coronaviruses (e.g., HCoV-NL63, SARS-CoV and SARS-CoV-2). CD BioSciences offers a complete portfolio of solutions for uncovering the mystery of receptors and sensors including identification and characterization of receptors and generation agonists and antagonists for receptors.

Signaling pathways transduce extracellular signals to affect transcription factor (TF) mediated gene regulation. TFs are sequence-specific DNA-binding proteins that control the transcription of DNA to mRNA. Approximately, 10% of genes in the human genome encode TFs, which makes them the single largest family of human proteins. <br> <br>The function of TFs is to regulate (turn on and off) gene transcription according to cellular signaling to make sure the right genes are expressed in the right amount on the right occasion. TFs work alone or with other proteins/cofactors to regulate a diversity of cellular processes, such as cell division, cell growth, metabolism, stress response and apoptosis. Mutations in TFs cause certain diseases. Thus, they are potential drug targets. <br> <br>The key to understanding the mechanism of a signaling pathway is to identify and characterize the TFs functioning downstream the signaling pathway. CD BioSciences offers a complete portfolio of solutions covering every aspect of TF studies, including binding motif analysis, domain mapping, and interacting protein identification.

Post-translational modifications (PTMs) are important components in signaling transductions, which affect the activity of proteins in signaling pathways. Phosphorylation is the most common PTM. The other PTMs include acetylation, methylation, glycosylation, lipidation, nitrosylation and ubiquitination. <br> <br>In signaling pathways, proteins exist in two states: activated and inactivated, which are generally under the regulation PTMs. PTMs mediate signaling transductions during cell proliferation and differentiation, immune response, metabolism, apoptosis, etc. Any dysregulation of PTMs in the cells leads to different levels of functional failures. Thus, learning how protein PTMs modulate signaling pathways are of great importance. <br> <br>CD BioSciences offers a complete portfolio of solutions for resolve PTM-related issues including PTM profiling, substrate and enzyme identification and inhibitor/activator screening.

Protein is a complex organic compound composed of amino acids. Due to the hydrophilicity, hydrophobicity, positive charge, negative charge and other characteristics of amino acid residues, it can be folded into a precise 3D structure through the interaction between the residues. The sequence of amino acids determines the unique 3D structure of each protein and its specific functions. Protein participates in almost every process in the cell and is necessary to maintain the structure and function of human tissues and organs. Protein folding errors can induce a variety of degenerative diseases, such as Parkinson&#039;s disease, Alzheimer&#039;s disease, frostbite, and senile heart failure. Therefore, imaging analysis of the folding process of proteins is of great significance for the early diagnosis and treatment of diseases.

Ubiquitination (ubiquitinylation) is a post-translational modification (PTM) process, where a ubiquitin is added to a lysine/cysteine/ serine/threonine of a substrate protein via the C-terminal glycine of ubiquitin. It is essential for balancing numerous physiological processes. Through altering proteins&#039; degradation, cellular location, activity, and interactions with other molecules, ubiquitination regulates protein functions in relevant signaling pathways.

Acetylation is one of the major protein modifications in cells, where the acetyl group from acetyl coenzyme A (acetyl-CoA) is transferred to a polypeptide chain. Protein acetylation can occur at N-terminal as a co-translational covalent modification by N-terminal acetyltransferases (NATs), or on lysine as a reversible post-translational modification (PTM). Like phosphorylation, acetylation also affects protein function by altering the properties of proteins such as hydrophobicity, solubility, protein conformation and affinity with other macromolecules.

Protein phosphorylation is a reversible post-translational modification (PTM) that acts as a molecular switch for many cellular events. The activation and deactivation of signaling pathways through phosphorylation by kinases or dephosphorylation by phosphatases are under delicate control.