What is the Difference Between Poly D Lysine and Poly L Lysine

The main difference between poly D lysine and poly L lysine is that poly-D-lysine is a type of polylysine made up of D-lysine while poly-L-lysine is the a type of polylysine made up of L-lysine. Furthermore, poly-D-lysine is more convenient for surface coating, facilitating the attachment of cells or proteins to solid surfaces while poly-L-lysine tends to be degraded by the enzymes secreted by several types of cells.

Poly-D-lysine and poly-L-lysine are two types of polylysine used in the surface coating of cell culture plates. The main function of polylysine is to facilitate the attachment, cell spread, growth, morphology, differentiation, and motility of cells.

Key Areas Covered

1. What is Poly D Lysine
     – Definition, Structure, Applications
2. What is Poly L Lysine
     – Definition, structure, Applications
3. What are the Similarities Between Poly D Lysine and Poly L Lysine
     – Outline of Common Features
4. What is the Difference Between Poly D Lysine and Poly L Lysine
      – Comparison of Key Differences

Key Terms

Cell Attachment, Polyamino Acids, Poly-D-Lysine, Poly-L-Lysine, Polylysine, Surface Coating

What is Poly D Lysine

Poly-D-lysine or PDL is a type of polylysine produced by the polymerization of D-lysine. Generally, polylysines are high molecular weight compounds that are positively-charged. Therefore, they pair with the culture surface, enhancing the electrostatic interactions between negatively-charged ions in order to increase the positively-charged sites available for cell binding.

Figure 1: Lysine Polymerization

Hence, the main function of polylysines in cell culture is to facilitate the attachment of cells to the cell culture surface, which can be either plastic or glass. And, this attachment facilitates cell spreading, growth, morphology, differentiation, and motility of cells whose growth, development, and attachment depend on the extracellular matrix components and exogenous attachment factors.

What is Poly L Lysine

Poly-L-lysine or PLL is a type of polylysine produced by the polymerization of L-lysine. However, the choice between poly-D-lysine and poly-L-lysine depends on the type of cell line used for cell culture. That means; some proteases produced by some cell lines can degrade poly-L-lysine. Generally, L-lysine is the biologically active form of lysine used in protein synthesis by living organisms.

Figure 2: Alpha-Polylysine

Therefore, proteases can degrade peptide bonds between poly-L-lysine. However, poly-D-lysine is nondegradable by such mechanisms. Thus, poly-D-lysine is more convenient with any type of cell line.

Similarities Between Poly D Lysine and Poly L Lysine

• Poly-D-lysine and poly-L-lysine are two types of polylysine, which is a polyamino acid used for the surface coating of solid surfaces of cell cultures.
• They are an exception to the serum proteins used by many regular cell culture techniques to facilitate the growth of the anchoring-depending cells.
• However, they do not stimulate any form of biological activity in cell culture.
• Also, they are positively-charged synthetic molecules.
• Furthermore, both are polymerization products of the optical isomers or the enantiomers of lysine.
• Moreover, they are high molecular weight compounds. More often, low molecular weight polymers tend to be degraded by the proteases secreted by cell lines.
• Besides, they both are metal-free polymers.
• They facilitate the attachment of cells and proteins to the plastic or glass surfaces.

Difference Between Poly D Lysine and Poly L Lysine

Definition

Poly-D-lysine refers to a type of polylysine produced by the polymerization of D-lysine while poly-L-lysine refers to a type of polylysine produced by the polymerization of L-lysine. Thus, this is the main difference between poly D lysine and poly L lysine.

Characteristics of the Monomer

Another difference between poly D lysine and poly L lysine is that D-lysine rotates the plane-polarized light clockwise while L-lysine rotates the plane-polarized light anticlockwise.

Conveniency

Moreover, poly-D-lysine is more convenient for surface coating while poly-L-lysine is less convenient for surface coating as some cell lines secrete proteases, which can degrade poly-L-lysine. Hence, this is another important difference between poly D lysine and poly L lysine.

Conclusion

Poly-D-lysine is a type of polylysine produced by the polymerization of D-lysine, which is the enantiomer of lysine, rotating the plane-polarized light clockwise. In comparison, poly-L-lysine is the other type of polylysine produced by L-lysine, the enantiomer of lysine, rotating the plane-polarized light anticlockwise. Though both types of polylysines are used for surface coating of cell culture surfaces to facilitate cell attachment, poly-L-lysine tends to degrade by proteases secreted by several cell lines. Therefore, poly-D-lysine is the convenient form of polylysine for some cell lines. Hence, the main difference between poly D lysine and poly L lysine is their convenience with cell lines.

References:

1. “Poly-Lysine Substrates for Cell Culture.” Cole-Parmer, Cole-Parmer, 15 Oct. 2018, Available Here.
2. “Poly-L-Lysine and Poly-D-Lysine.” Poly-L-Lysine and Poly-D-Lysine | Alamanda Polymers – Polyamino Acids, Superior by Design, Available Here.

Image Courtesy:

1. “Polylysine derivatives” By Oregonpillow – Own work (CC BY-SA 4.0) via Commons Wikimedia   
2. “Alpha-Polylysine” By HyperGaruda (talk) – Own work (Public Domain) via Commons Wikimedia