What is a nano machine? A nanomachine is an organelle that consists of many small components, each of which has a unique function and is powered by ATP. These components are assembled on AuNP and show excellent intramolecular reaction control, which is important for enhancing the speed of motion. In the complex environment of a cellular ecosystem, such complex interactions would impede easy access to essential components and would lead to low productivity. In this way, a DNA nanomachine is a unique example of elegantly assembling components and using intracellular biomolecules as its driving force.
ATP is the fuel of a nanomachine
To make a nanomachine, researchers are using a basic principle from the human body: ATP. ATP is a compound found in all living organisms that powers the many processes occurring within each cell. It spins hundreds of times per second, and is the energy carrier for many cellular functions. Scientists have used this compound to build nanomachines and have already successfully demonstrated its use in cell signaling.
ATP is composed of two molecules: a purine base known as adenine and the sugar ribose. Together, these molecules form the nucleoside adenosine. They are connected by a phosphate ester bond. This structure allows ATP to release energy only when an enzyme is present to catalyze the reaction. Until recently, scientists believed that ATP could be the fuel for nanomachines.
It is also possible to design nanomachines that can function without ATP. In many ways, nanomachines operate like a real-life machine, and ATP is the fuel. But unlike a human-made machine, the structure of a nanomachine is more complex. And this complexity is irreducible. Scientists have discovered four basic ways to create ATP: through bacterial cell walls, chloroplasts, and mitochondria. But how does a human-made nanomachine use a single-molecule ATP?
DNA twists can make a nanomachine
Molecular machines made from DNA are a promising method for executing diverse biological tasks. Nanomachines can be incorporated into cells and driven by endogenous force, making them useful for a wide range of applications. This paper describes how DNA twists can produce a bioanalytical system with the capability to image specific microRNAs. In vivo applications of DNA nanomachines are also expected to be a reality soon.
DNA carries a high degree of specificity, meaning that DNA binds to its complementary sequence. This quality can be useful for designing nanomachines, especially when combined with sensors. Single stranded DNA binds to a double-helix or triple-helix when exposed to a specific environment. Such a combination of sensors could result in a smart drug delivery system. For these reasons, many researchers have focused on using DNA as a model for molecular machines.
Despite its toughness, DNA is flexible and programmable. The researchers used a combination of targeted base pair insertions and deletions to give DNA bundles the desired twist. The result is a machine that can control the shape of its parts with a fine degree of precision. The researchers report that the new machine can even perform tasks involving complex mathematics. It is still unknown whether this new DNA machine will ever be used for manufacturing, but the possibilities are exciting.
Functions of a nanomachine
Nanomachines are small, computer-like devices. Their rigid components convert energy and transfer forces in one specific direction. Their goal is to perform useful tasks and produce work. Unlike simple machines, nanomachines have three basic requirements for a functional system:
As a unit of information processing, a nanodevice needs to have a memory. It may use its memory to store a set of instructions or to maintain configurations. Some nanomachines do not need a memory. Some have molecular components that act as long-term memory. Others use their cytoplasm for this function. Some nanomachines may also have multiple functional units, like a network of proteins.
Sensors interact with the environment by collecting changes in physical, chemical, or biological properties. Actuators are a second type of sensor. They respond to the data they sense by manipulating their environment. Biological cells use cilia as sensing antennas, while nanomachines are made by reprogramming biological materials or artificially synthesizing biomolecules. In the process of fabricating nanomachines, many important factors must be taken into consideration, including size, shape, and biodegradability.
DNA nanomachines are programmable, and they can function in living organisms. These nanomachines can be built from mRNA and DNA and function in both cellular and organismal milieus. Interestingly, in vitro functionality does not imply in vivo functionality. In fact, molecular complexity increases dramatically from in vitro to in cellulo and from in vitro to in vivo boundary.