Detection of spider silk formation mechanism

(Khoahoc.tv) - Spider silk is a very special material, it is lightweight and highly elastic but stronger than steel. However, the challenge that spiders face to produce this substance is even more terrible.

Spider silk proteins , called spidroins , must convert a liquid form into a solid fiber at ambient temperature, along with water as a solvent, and at very high speeds. How do spiders do this amazing thing?

In a new study presented on the open access of PLOS Biology magazine on August 5, 2014, Anna Rising and Jan Johansson showed how the process of silk formation takes place. This study was conducted at the Swedish University of Agricultural Sciences (SLU) and Karolinska Research Institute in collaboration with colleagues in Latvia, China and the United States.

Spidroins are large proteins with up to 3,500 amino acids that contain mainly repetitive sequences, but the most important parts for the spidroin transformation into silk are at the end . These last regions of proteins are unique to spider silk and are very similar among different spiders.

Spidroins have a twisted and unordered structure when stored as soluble proteins in silk glands, but when converted into silk, their structure changes completely into a structurally stable structure. high school These changes are triggered by an acidity gradient (acidity gradient) that occurs between a tail of the gland and other silk glands.

The silk gland comes from a narrow end to a pouch and to a delicate duct, and scientists know that spider silk forms at a precise location inside the duct. However, more specific details about spider silk production are still difficult to understand.

By using highly selective microelectrodes to measure pH in silk glands, the authors have demonstrated that pH has decreased from neutral pH to 7.6 to 5.7 acid pH between the first and last and the lower half of the tube, and the pH gradient are much higher than scientists think.

Microelectrodes also show that the concentration of bicarbonate ions and pressure of CO2 also increase along the silk route. Together, these factors have shown that the pH gradient can be formed through the activity of an enzyme called carbonic anhydrase , which converts carbonic and water into bicarbonate and hydrogen ions (and thus creates the environment Acidic).

Using a method developed by the authors, the researchers were able to determine activated carbonic anhydrase weighting a narrower part of the silk gland and determining that carbonic anhydrase was actually responsible for causing the pH gradient.

The authors also found that pH had an opposite effect on the stability of the two regions at the end of the spidroin proteins, which is surprising that these regions were thought to have similar roles in shaping silk. While part ends (top end N) tends to pair with other molecules at the tip of the tube and becomes stable when the acidity increases along the tube, the other end (end of C) is unstable when acidity increases, and spreads until it forms the silk's structural properties at a pH of 5.5. These findings demonstrate that at the top of the tube is also the point where carbonic anhydrase activity is concentrated.

These insights led the researchers to propose a new 'lock and activation' model for the formation of spider silk, which gradually formed pairs of N ends of spidroin into a network of protein molecules, while structural changes in the end of C can activate the polymerization of spidroins into 'amyloid' fibers (starch) found in the brains of People with diseases like Alzheimer's disease.

This mechanism helps explain why slender spider silk can form quickly and smoothly in the ductile tube of this magical creature. In addition to humans being able to imitate spiders to produce biomimicry spidroin fibers for our purposes, this study also helps provide insight into how starchy fibers are hindered in a way Naturally related to diseases such as dementia in humans.