Welcome back to my magic flying carpet –
PHFA (He..he! haa..haa! Positive Health For All!)
to see more of prions, viroids, viruses, bacteria etc.,
in ascending order of size.
Before diving deeper into the study of OUR prions,
a note of disambiguation.
The word “Prion” may mean different things to
different people depending on their calling /
profession / interests.
An Ornithologist / Bird Expert / bird watcher / birder
(a subset of zoologists studying birds) will think
of the Prions in Ornithology lingo – the whalebirds
which are small petrels in the genera Pachyptila
and Halobaena. They form one of the four groups
within the Procellariidae (also referred to as the
prions), along with the gadfly petrels, shearwaters
and fulmarine petrels. They are found in the
Southern Ocean and breed on a number of
subantarctic islands. Prion Birds grow 20–27 cm
(7.9–11 in) long, and have blue-grey upper parts
and white underparts. Three species of prion
birds have flattened bills with a fringe of lamellae
that act as strainers for zooplankton. All prion
birds are marine and feed on small crustacea
such as copepods, ostracods, decapods, and
krill as well as some fish such as myctophids
and nototheniids. So ornithologists have been
using the name Prion for a long long time –
decades, nay centuries, long, long before the
Prions, the subjects of this page, came to be
noticed and named Prions in 1982!
A Google search for “Prion” also yielded results
about an industrial group PRION GmbH PLM & IT
Solutions of Germany providing engineering /
industrial software solutions. GOK why the
company chose this special name! Look them up
if you need their services.
A footwear company called ThirtyTwo selling Boots,
Outerwear and Apparel for men calls a stylish model
of their boots “Prion”, GKW!
Prions, which are the subject of this page, got their
novel name in 1982 from Nobel Laureate,
Prof.Stanley Benjamin Prusiner, an American
neurologist and biochemist, currently the
Director of the Institute for Neurodegenerative
Diseases at University of California, San Francisco
(UCSF). Prusiner derived the name Prion, for his
newly – found pathogenic (disease – producing / Killer
/ Rogue) proteins, coined from the words protein and
infection – From (a reordering of) the initial letters of
proteinaceous infectious particle – Prions short for
“proteinaceous infectious particles (-ions – a suffix
that occurs in virion etc.,)”. A prion is an infectious
agent that is composed primarily of a single protein
(albeit modified / misfolded protein PrP (Prion Protein)) –
almost similar to the normal (folded) proteins
normally occurring in all living beings but devoid of
nucleic acids like DNA and RNA which carry genetic
information and are essential for replication /
multiplication / reproduction and hence are present
in higher pathogens like viruses and bacteria and
all living beings oncluding humans.
But Prions, though not living and not capable of
spontaneous reproduction, are still easily transmissible
particles causing fatal diseases.
Now that you know the chemistry of Prions, let us see
some of their physical characteristics – their size,
their susceptibility or resistance to isolation and
destruction, and physio – pathological characteristics
of destructivity / pathogenicity / morbidity / killer
Prions are tiny, miniscule particles measuring in the
nanometer range – Prions measure 10 nm while the
recently synthesised Miniprions measure 5- to 10-nm;
the only known particle smaller than MiniPrions is
DNA which measures 2 nm(diameter of a single strand).
proteins measure 5 – 50 nm; ribosome neasures 25 nm;
viruses measure 20 – 100 nm; mitochondria measure
1µm diameter x 2 µm length; bacteria measure 1 – 5 µm;
human cells measure 10 – 100 µm.
No wonder, Prions and MiniPrions can be seen only
with electron microscope (Negative-stain) and electron
crystallography and may need nuclear magnetic
resonance spectroscopy for characterisation.
Prions and MiniPrions are insoluble in known / common
solvents and hence defy extraction.
Prions and MiniPrions defied isolation by the less
sophisticated ultracentrifugation and ultrafiltration
devices passing through 0.1 µm filters (2.2 µm filters
remove bacteria) available in the years of Prion
discovery. The more recent tangential filtration
devices (like Ultrasette, Filtron, Northborough, MA)
used in a continuous mode and ultracentrifugation
devices like Beckman Optima L80 ultracentrifuge
(Beckman Coulter Inc., Fullerton, CA) have made
present researchers’ work a lot easier.
Can Prions be destroyed by any method available?
You cannot kill what is not live! Prion are not live
and hence defy killing! Prions cannot be destroyed
by boiling, alcohol, acid, standard autoclaving
methods, or radiation (UV and X – ray included).
In fact, infected brains that have been sitting in
formaldehyde for decades can still transmit Prion –
caused spongiform disease. Cooking your burger
’til it’s well done won’t destroy the prions! Prions are
extremely resistant to heat and to normal
sterilization processes. Prions do not evoke a
detectable immune response or inflammatory
(Heat / fire) reaction in host animals. For the same
reason that cells can not destroy prion protein , prions
are very heat resistant. Some loss of infectivity is said to
occur at temperatures above 100°C. But 30 to 60
minutes at more than 130°C is needed for inactivation,
although autoclaving at 134°C to 138°C for 60 minutes
does not result in complete inactivation. Prions remain
infective after sterilizing levels of radiation, formalin
exposure, extremes of pH, non-polar organic solvents,
burying for years and even cremation at 343°C
or 360°C. Prions infectivity is destroyed by 1M NaOH
@ 55°C or chlorine bleach @ 20,000 ppm (household
bleach is 50,000 ppm). Exposure for two hours to a
sodium dichloroisocyanurate solution (16,000 ppm
of available chlorine) did not completely deactivate
prions’ infectiveness. Homogenates of Prion -BSE –
infected bovine brain and rodent brain infected
with prion – scrapie – agent and exposed to 2M sodium
hydroxide for two hours did not inactivate the prion
agents. High – infectivity hamster – adapted prion
disease – scrapie is extremely resistant to heat,
chemicals, and processing!
So for all practical purposes, at least as on date,
Prions are indestructible!
Indestructible as prions are, they are highly,
terribly destructive to all living beings!
More on that at a later page!
So long! Sleep well! Let there be no nightmares of
prions killing you!