chirality Archives

September 19, 2025September 18, 2025

The Homochirality of Organic Molecules

Yesterday, we discussed the chirality, or handedness, of molecules, especially amino acids and proteins. The homochirality of organic molecules refers to their requirement for the same handedness, a mystery that has puzzled scientists since 1848, when Louis Pasteur first observed that some life-essential molecules had mirror-image forms. Amino acids used by living cells and the proteins they build have left-handed chirality, while DNA, RNA, and the sugars forming their building blocks are all right-handed. These facts raise a question for those who believe life arose spontaneously.

Left-handed proteins and right-handed DNA are found in all living organisms. The spiral structure of DNA needs to twist in a specific direction to function properly, but what caused the right-handed sugar molecules to come together? When half of all amino acid molecules in nature exhibit right chirality and the other half left, what force could have gathered only the left-handed ones to form the first proteins?

Scientists have speculated that cosmic rays or polarized light might have triggered this process. However, even if such forces created an initial bias for the same-handedness, they could not sustain and amplify it enough to produce a significant number of homochiral molecules to form the first living cells. In 1999, researchers proposed that electron spin created magnetism, causing left-handed peptides (short chains of amino acids) to bind to magnetic surfaces like magnetite. But this still did not explain how the homochirality of organic molecules could be amplified sufficiently to generate living cells.

Some scientists consider RNA to be the key to the origin of life. In 2009, a group of researchers studying RNA molecules suggested that a crystal called RAO could react to produce two of RNA’s four nucleotides. In 2023, other researchers used magnetism to produce RAO crystals with homochirality. However, this process required a magnetic field 6,500 times stronger than Earth’s magnetic field. Additionally, RAO has only been shown to produce two of RNA’s four nucleotides, still falling short of generating the complete homochirality of molecules needed for life.

As 2024 ended, NASA-funded research identified a problem with the so-called “RNA world” hypothesis. Simulating early Earth conditions, they found that RNA did not show a chemical bias toward selecting homochiral amino acids. The current thinking is that the homochirality of organic molecules “could have emerged through later evolutionary pressures.” In other words, we have the “evolution-of-the-gaps” theory because, of course, evolution can do anything you can imagine.

Currently, NASA scientists are analyzing samples brought back from asteroid Bennu, hoping that molecular evidence from meteorites and asteroids will demonstrate that the building blocks for life came from beyond Earth. I suspect that the force responsible for bringing life to Earth did originate outside our planet, and even beyond the universe.

References: science.org and nasa.gov

September 18, 2025September 18, 2025

Left-Handedness of Proteins and Amino Acids

About 9.2 percent of people are left-handed. In other words, less than 10 percent of humans exhibit left-handedness. However, the proteins in living organisms are 100 percent left-handed. I know proteins don’t have hands, but using the term “handedness” helps to explain how proteins are structured. Proteins are made from amino acids, which fold into left-handed shapes that enable their functions in living beings. These proteins are composed of amino acids, which are also left-handed.

This handedness is more accurately called “chirality.” There are over 500 different amino acids, and they exhibit both left and right chirality. However , only 22 of them are used to make proteins, and their chirality is all left-handed. This creates a mystery. If amino acids existed on early Earth in equal amounts of right- and left-handed forms, and life requires only left chirality, how could life have formed spontaneously? Some thus-far unexplained force would have to select only left-handed amino acids to come together to get life started. Robert F. Service, writing on science. org, called this “an enduring mystery.”

Scientists have proposed several ideas to explain why proteins are left-handed. Some suggest meteorites delivered left-handed amino acids to early Earth. It appears that meteorites are rich in these amino acids, likely due to exposure to polarized light. Another hypothesis is that magnetic fields on early Earth twisted the biomolecules. Robert Service asks, “But even if some external force imparted an initial bias, what propagated it?”

Gerald Joyce, a chemist specializing in the origins of life and president of the Salk Institute for Biological Studies, said, “Perhaps it was just a statistical coin flip that caused an original bias toward building blocks of one-handedness to form. But once that coin flipped, it caused other coins to flip.” Those of us who believe in a Creator are often accused of using a “God-of-the-gaps” explanation for life’s mysteries. To me, this explanation for the left-handedness of proteins sounds like a “coin-flip-of-the-gaps.”

Reference: science.org and Science magazine, Vol 383, Issue 6686

August 24, 2023August 23, 2023

The Problem of Homochirality

Can life arise spontaneously from non-living chemicals? Scientists have spent many hours and vast amounts of research money attempting to prove it can. One of the many challenges they must solve is the problem of homochirality.

All the large molecules required to make a living cell are composed of building blocks that have mirror images. When you look in a mirror, you see a reversed image of yourself. The right hand appears to be on the left and vice versa. The right- and left-hand analogy is used when referring to the building blocks of life. Those building blocks come in either right or left-handed forms. We call that handedness “chirality” from the Greek word for hand. Homochirality means having the same handedness.

Life almost exclusively uses only one chirality. The amino acids that make up proteins are left-handed. Scientists are uncertain why, but they have to accept the fact that to build the proteins that RNA and DNA molecules require for life, you must have only left-handed amino acids.

In nature, amino acids are not homochiral. They come in a distribution of about 50/50 left and right, creating the problem of homochirality. For amino acids to form the building blocks of life, they would have to be homochiral. Scientists have yet to find a way to make that happen, even in the laboratory. They aren’t even sure why life requires it since the chemical properties of mirror-imaged compounds are the same for all practical purposes.

The problem of homochirality is one of the many obstacles that prevent non-living chemicals from coming together to form life without intervention by an intelligent force. Even the intelligence of our best scientists has not overcome those obstacles. I saved an Associated Press news release from 2007 titled, “Scientists Believe Artificial Life Will Be Possible in 3 to 10 Years.” We are well past that goal, and I suspect they are not much closer today.

August 24, 2017August 17, 2023

Origin of Life Problems Admitted

Wing Challenge to Origin of Life
One of the more honest and fair writers in modern scientific publications is Dr. Bob Berman. He has a regular column in Astronomy magazine and an interesting website. In the September 2017 issue of Astronomy (page 10), he has an outstanding brief review of the problems involved in trying to explain the origin of life. He begins by pointing out that the definition of “life” has been an issue because of questions such as whether or not a virus is alive. Viruses have no metabolism, they don’t feed or breathe, and yet they reproduce.

Berman then reviews some of the parameters necessary to consider when addressing the origin of life. Chirality is a major issue because amino acids that make up proteins come in right- and left-handed versions. Life on Earth is made up of only left-handed amino acids. Sugars used by the proteins are limited to the right-handed direction, and so is DNA. The wrong chirality just will not work to support life, so how could nature sort out the chirality? If life is easy to produce, why don’t we see it coming into existence all over the Earth? The “amoeba-to-man” model assumes that it only happened once, which conflicts with the view that life is abundant in the cosmos.

What is especially interesting is that Berman raises questions about the ability of evolution to explain on a chance basis some of the designs we see in living things. He uses the example of the airfoil that all flying forms of life have. The upper surface is convex using the Bernoulli effect to produce lift. The earliest bird and the flying reptiles all had a wing design that works. Trial and error would not work well to explain how the wing design would come into existence by chance. Berman points out that “some 400,000 cells would all have to simultaneously mutate in just the right way to create a properly shaped wing. This defies an evolutionary hypothesis.”

Berman concludes with the statement, “I’m not invoking spirituality, merely that the effect of random collisions and mutations is not always a workable answer. So perhaps nature is inherently smart.” I would suggest that wing design is just one of a massive number of design features that allow life to exist.

Berman quotes Francis Crick, the co-discoverer of DNA’s double helix as saying that the origin of life is “almost a miracle, so many are the conditions which would have had to have been satisfied to get it going.” We don’t invent a “god” to explain these things, but we would point to these things as one more evidence that there is a God and that blind chance is not a good designer of the complexity we see in the world around us.
–John N. Clayton © 2017