What is the biggest molecule? PG5, DNA and molecules in space

The largest synthetic molecule with a defined, persistent shape is PG5, a giant branched polymer with a molar mass of about 200 million grams per mole (200 megadaltons) and roughly 17 million atoms. By mass, though, natural DNA is far bigger: the DNA in a single human chromosome 1 is roughly 800 times heavier.

So the answer depends on what “biggest” means. Molecules can be ranked by mass, length, width or number of atoms. Synthetic chemistry, biology and astronomy each have their own record holders, and they are not directly interchangeable.

Key facts about the biggest molecules

• Largest synthetic molecule with a defined shape: PG5, a fifth-generation dendronized polymer reported by an ETH Zurich team in 2010–2011
• PG5 size: about 200 megadaltons, about 17 million atoms, about 10 nanometres wide and up to a few micrometres long
• Largest by mass in your body: chromosomal DNA. Chromosome 1 carries about 249 million base pairs, roughly 1.5–1.7 × 10¹¹ daltons and about 8.5 cm of DNA if stretched out
• Largest molecules confidently identified in space: the carbon cages C₆₀ and C₇₀, first detected in 2010
• Why definitions matter: polymer chains vary in length, so “one molecule” of PG5 or DNA has no single fixed formula

What is PG5?

PG5 is not a single compact molecule like water, caffeine or buckminsterfullerene. It is a dendronized polymer: a long molecular backbone carrying densely packed, tree-like branches called dendrons.

Those branches are added in successive generations. PG5 is the fifth generation, so its exterior is exceptionally crowded. The crowding forces the chain into a relatively stiff cylinder instead of letting it coil freely like many ordinary polymers.

A team led by A. Dieter Schlüter at ETH Zurich reported the structure in Angewandte Chemie, published online in December 2010. They built the branches layer by layer around a polymer backbone. According to the team, the result was a molecule about 10 nanometres across and, for the longest chains, up to a few micrometres long.

How long and wide is a PG5 molecule?

Every part of a PG5 chain is joined by covalent bonds into one connected structure. That is why chemists can call an individual chain a molecule even though it is long enough to see with electron and atomic-force microscopes.

Its proportions are extreme: only about 10 nanometres wide but up to a few thousand nanometres long. A scale model shows what that means.

Worked calculation: PG5 as a drinking glass

• Take a chain 10 nm wide and 3 μm (3,000 nm) long. Its length is 3,000 ÷ 10 = 300 times its width.
• Enlarge it until its width matches a typical drinking glass, about 8 cm across.
• Its length becomes 300 × 8 cm = 2,400 cm, or about 24 metres.

Shorter chains give proportionally shorter models, so a realistic range is a few metres to a few tens of metres. PG5’s measured width also changes with how the sample is prepared and measured. Treat the model as a picture of proportions, not an exact replica.

Does PG5 have a chemical formula?

Not one simple, universal formula.

Small molecules usually contain a fixed number of atoms and have a fixed formula. A polymer sample contains chains with a distribution of lengths. Chemists therefore describe PG5 using the formula of its repeating unit together with an average number of repeats, written as n.

The backbone polymer used to build the record sample averaged about 10,600 repeat units, according to the ETH Zurich team. A different batch or chain may differ. For the same reason, “200 megadaltons” describes the largest reported material, not a claim that every PG5 chain has exactly the same mass or atom count.

Is DNA bigger than PG5?

Yes, by mass and by length. PG5 is only wider.

Human chromosome 1 is the longest human chromosome. In the current reference genome (GRCh38), its assembled sequence is 248,956,422 base pairs. Each base pair adds about 0.34 nm of length and roughly 618–665 daltons of mass, depending on the reference value used.

• Length: 248,956,422 × 0.34 nm ≈ 8.46 × 10⁷ nm ≈ 8.5 cm
• Mass: 248,956,422 × (618 to 665 Da) ≈ 1.5–1.7 × 10¹¹ Da
• Compared with PG5: 1.5–1.7 × 10¹¹ ÷ 2 × 10⁸ ≈ 770–830 times heavier

There is one subtlety. A DNA double helix is two strands held together by hydrogen bonds, not by covalent bonds. If “one molecule” means one continuous covalent chain, each strand of chromosome 1 still carries about half that mass, which is still roughly 400 times PG5. That DNA sits, tightly packaged, in the nucleus of each human cell; our guide to how plant and animal cells differ explains where it lives.

PG5’s distinction is therefore narrower but still real: it is a synthetic molecule built with deliberate control over its shape at an enormous size.

What is the largest molecule found in space?

The largest molecules confidently identified in space are fullerenes, the football-shaped carbon cages C₆₀ (60 carbon atoms) and C₇₀ (70 carbon atoms). In 2010 Jan Cami and colleagues reported their infrared signatures in a planetary nebula called Tc 1, using NASA’s Spitzer Space Telescope.

In 2015 Ewen Campbell, John Maier and colleagues matched laboratory spectra of the positively charged ion C₆₀⁺ to two long-unexplained absorption features in starlight, known as diffuse interstellar bands. That showed the ion is present in the space between the stars.

These cages are huge by space-chemistry standards but tiny next to PG5. C₆₀ has a mass of about 720 daltons, so a 200-megadalton PG5 chain is roughly 280,000 times heavier.

Which molecule is biggest? It depends on the definition

Sources: ETH Zurich Schlüter group (PG5); NCBI Genome Reference Consortium GRCh38.p14 (chromosome 1 length); BioNumbers (0.34 nm rise per base pair; 618 and 665 Da per base pair in different entries); Cami et al. (2010) and Campbell et al. (2015) for space fullerenes. Masses for DNA, C₆₀ and C₇₀ are SciQuest calculations from these values and the atomic mass of carbon (12.011 Da).

Why did scientists make PG5?

The project was not simply a contest to create a record. Dendronized polymers bridge the gap between conventional molecules and nanoscale objects. Their controlled dimensions may help researchers study molecular transport, nanoscale templates, host–guest chemistry and the limits of precision polymer synthesis.

Possible applications are research directions, not established consumer technologies. PG5 matters mainly because it shows how much complex architecture chemists can build using covalent bonds.

Frequently asked questions

Is PG5 bigger than DNA?

No, not by mass or length. A single human chromosome 1 DNA molecule is roughly 800 times heavier than PG5 and about 8.5 cm long when stretched out. PG5 is much thicker, at about 10 nm across, and it is the record holder among synthetic molecules with a controlled shape.

Is PG5 visible to the naked eye?

No. Even a micrometre-long molecule is far below the unaided eye’s resolution. Scientists study PG5 using electron and atomic-force microscopy, scattering techniques and chemical analysis.

Is C60 the biggest molecule?

No. C₆₀, made of 60 carbon atoms, is famous and highly symmetrical, and with C₇₀ it is among the largest molecules identified in space. At about 720 daltons, though, it is tiny next to giant polymers such as PG5 or DNA. For the building blocks involved, see the parts of an atom.

The short answer

PG5 is the record holder for the largest synthetic molecule with a defined, shape-persistent architecture, at about 200 megadaltons and 17 million atoms. Natural chromosomal DNA is far heavier and longer, and in space the largest securely identified molecules are much smaller carbon cages like C₆₀ and C₇₀.

Related reading

• Imaging the DNA double helix with self-blinking probes
• Can identical twins have the same DNA?
• How plant and animal cells differ

Update note: This article was substantially revised and fact-checked on August 23, 2026, to clarify PG5’s record, dimensions and polymer chemistry. On October 12, 2026, it was updated to correct the drinking-glass scale model (tens of metres, not hundreds), state clearly that chromosomal DNA is far larger than PG5 by mass and length (with worked numbers), add the largest molecules identified in space (C₆₀ and C₇₀), remove dimension figures we could not verify, correct a misattributed citation and add internal links. It was drafted with AI assistance and checked against the sources listed below.

Sources

• Schlüter research group archive, ETH Zurich, The largest synthetic molecule
• Zhang, B. et al., The Largest Synthetic Structure with Molecular Precision: Towards a Molecular Object, Angewandte Chemie International Edition 50, 737–740 (2011; published online December 2010)
• Phys.org, Giant molecule synthesized (January 2011)
• NCBI Genome Reference Consortium, GRCh38.p14 human assembly data
• BioNumbers, DNA helix rise per base pair (BNID 100667), Molecular mass of DNA base pair (BNID 100304) and Mass of DNA in exponentially growing E. coli B/r cell (BNID 104908, which uses 618 Da per base pair)
• Cami, J. et al., Fullerenes in circumstellar and interstellar environments (review of the 2010 Science detection of C₆₀ and C₇₀ in Tc 1)
• Campbell, E. K. et al., Laboratory confirmation of C₆₀⁺ as the carrier of two diffuse interstellar bands, Nature 523, 322–323 (2015)