Protein spiral and the transfer of DNA fragments to cells

The group of researchers led by Professor Jianjun Cheng and Professor Fei Wang, working at the University of Illinois, USA, have shown that: spiral-shaped proteins are short-lived in favor of providing DNA fragments to cells. The results of this study were published in the journal Angewandte Chemie.

"The main idea is to create new materials that could potentially be used in clinical gene therapy , " said Jianjun Cheng, a professor of materials and engineering science, chemistry and biotechnology. .

Researchers have discovered two main ways of transferring genes: regulating viruses and non-viral agents such as synthetic resins or lipids (lipids). Considering both the toxicity and the performance, the Polypeptide , also known as the short spiral protein chain , is an attractive material because of its properties: biocompatible, easy to navigate and size. small.

"Although vitrotransfection agents are available, we cannot use them in vivo because of their toxicity and size , " Cheng said. "Using polypeptides, we can control the size down to the threshold of 200nm (nano meters), forming a system that provides DNA fragments for living organism applications."

Polypeptide also known as poly-L-lysine (PLL) is a leading candidate in gene distribution studies. The positively charged PLL in the molecular structure chain comes from each amino acid bond in the polypeptide chain, so PLL can be dissolved in the humid environment of the cell.

However, PLL has gradually been removed because of its limited ability to introduce genes into cells, (a process known as transformation), and by high toxicity. Professor Cheng postulated that the low efficiency of the PLL could be due to the function of the spherical shape, making the polypeptide chain tended to receive a random entanglement structure, instead of an ordered spiral chain. than.

In early 2011, Professor Cheng's team developed a method of making short spiral polypeptides with positively charged side chains. To test whether a short spiral polypeptide could be an effective gene transfer agent, the researchers assembled a stable series of 31 polypeptide helices over a wide pH range and were able to transfer DNA fragments to cell. Most short spiral polypeptides work better than PLLs and some short spiral polypeptides also work better (both polyethyleneimine (PEI) agents, which are well known for their high toxicity even though they work well). This kernel works very well. These short spiral polypeptides also work well on some cells such as stem cells and fibroblasts.

"The polypeptides that we designed, synthesized and used in this study have very high efficacy and well controlled toxicity. With a modified spiral polypeptide, we have demonstrated that a polypeptide Short spiral can work better than many other trade agents, " said Professor Cheng.

Professor Cheng's team can create polypeptides with a variety of spiral designs because the lateral chains are longer, so that positive charges do not interfere with protein meandering. Positive charges are easily linked to negatively charged DNA, forming complex clusters that are absorbed into the cell cavity known as intracellular organs, to deliver DNA segments to cells.

To determine: short spiral-shaped polypeptides are the key to the transformation process, the researchers synthesized the two most effective polypeptide waves: one with short spiral-shaped polypeptide; a batch with random polypeptide rolls. The results confirmed: short spiral-shaped polypeptides far beyond random polypeptide rolls in terms of performance and stability.

"This proves that spiral shapes are very important, because polymers have the same chemical composition, but they will have different properties due to different structures " , according to Professor Cheng, who is collaborating with the Institute of Genetic Biology and the Beckman Institute of Applied Science and Technology, University of Illinois, USA.

In the near future, researchers plan to continue to explore the properties of short spiral polypeptides, especially the ability to penetrate cells. The researchers hope to control high-precision short-spiral polypeptide sequences and structures in specific applications, including: providing DNA fragments for cells, drug delivery, membrane invasion cells and antibacterial.