rôle du zinc
Posté : 30 mars 2006 10:28
New Metal Detector to Study Human Disease: Zinc Research
ProHealthNetwork.com
03-27-2006
Source: American Chemical Society
Zinc may be a familiar dietary supplement to millions of health-conscious
people, but it remains a mystery metal to scientists who study zinc's role
in Alzheimer's disease, stroke and other health problems.
They are just beginning to fathom how the body keeps levels of zinc under
the precise control that spells the difference between health and disease.
Researchers now have developed a biochemical metal detector to help crack
the mystery. It is a biosensor that has yielded the first measurements of
the tiny amounts of zinc ordinarily present inside living cells.
The study appears in the current issue of ACS Chemical Biology, the newest
of 34 journals published by the American Chemical Society, the world's
largest scientific organization.
It was conducted by Rebecca A. Bozym and Richard B. Thompson, Ph.D. of the
department of biochemistry and molecular biology, University of Maryland
School of Medicine, Baltimore, and Andrea K. Stoddard and Carol A. Fierke,
Ph.D. of the Department of Chemistry, University of Michigan, Ann Arbor.
"The question of how much zinc is available in a cell has emerged at the
forefront of chemical biology," Amy R. Barrios, Ph.D., of the University of
Southern California, Los Angeles, wrote in an accompanying Point of View in
ACS Chemical Biology.
Barrios described the new research as "a critical step forward," and
predicted "many more exciting breakthroughs" in measuring levels of metals
in human cells.
Just 2-3 grams of zinc (the weight of a penny coin) exist in the entire
human body. The metal is a key building block in enzymes and other
substances involved in functioning of the nervous system, the immune
response, and the reproductive system.
"We believe this new technique can help us understand how zinc is involved
in plaque formation in Alzheimer's disease, how prolonged seizures or stroke
kill brain cells, and how the cell normally allocates zinc to different
proteins," said Thompson.
Thompson explained that almost all zinc inside cells is incorporated into
proteins, where it plays many vital roles, such as helping to read the
genetic code of DNA.
"We know that if there is much zinc in the cell that is not attached to
protein or otherwise encapsulated - so-called 'free zinc' -the cell is
stressed or may be undergoing programmed cell death. This has been observed
in animal models of epilepsy and stroke."
In the past, scientists could only measure the relatively high levels of
zinc in sick cells. The new sensing technology can measure very low free
zinc concentrations in healthy cells.
The technique uses a special protein molecule that has been re-engineered to
report when zinc becomes stuck to it as a change in luminescence that can be
seen in the microscope. This protein (originally found in blood cells) is
very selective, recognizing tiny levels of free zinc even in the presence of
the million-fold higher levels of other metals present in cells, such as
calcium or magnesium.
Because proper zinc levels are so important in health and disease,
scientists have been seeking ways of measuring zinc inside and outside of
cells for more than a decade.
"This is an important discovery," said Sarah B. Tegen, Ph.D., managing
editor of ACS Chemical Biology. "We need to know how the body controls
levels of zinc inside cells. Too much zinc can kill nerve cells. With too
little, nerve cells will not work properly.
"Now we have a metal detector, technology that can measure tiny amounts of
zinc in living cells. Understanding how zinc is stored and released in
different cells throughout the body may help us understand some of the nerve
damage that occurs during a stroke and other nerve injuries."
- Michael Woods
ProHealthNetwork.com
03-27-2006
Source: American Chemical Society
Zinc may be a familiar dietary supplement to millions of health-conscious
people, but it remains a mystery metal to scientists who study zinc's role
in Alzheimer's disease, stroke and other health problems.
They are just beginning to fathom how the body keeps levels of zinc under
the precise control that spells the difference between health and disease.
Researchers now have developed a biochemical metal detector to help crack
the mystery. It is a biosensor that has yielded the first measurements of
the tiny amounts of zinc ordinarily present inside living cells.
The study appears in the current issue of ACS Chemical Biology, the newest
of 34 journals published by the American Chemical Society, the world's
largest scientific organization.
It was conducted by Rebecca A. Bozym and Richard B. Thompson, Ph.D. of the
department of biochemistry and molecular biology, University of Maryland
School of Medicine, Baltimore, and Andrea K. Stoddard and Carol A. Fierke,
Ph.D. of the Department of Chemistry, University of Michigan, Ann Arbor.
"The question of how much zinc is available in a cell has emerged at the
forefront of chemical biology," Amy R. Barrios, Ph.D., of the University of
Southern California, Los Angeles, wrote in an accompanying Point of View in
ACS Chemical Biology.
Barrios described the new research as "a critical step forward," and
predicted "many more exciting breakthroughs" in measuring levels of metals
in human cells.
Just 2-3 grams of zinc (the weight of a penny coin) exist in the entire
human body. The metal is a key building block in enzymes and other
substances involved in functioning of the nervous system, the immune
response, and the reproductive system.
"We believe this new technique can help us understand how zinc is involved
in plaque formation in Alzheimer's disease, how prolonged seizures or stroke
kill brain cells, and how the cell normally allocates zinc to different
proteins," said Thompson.
Thompson explained that almost all zinc inside cells is incorporated into
proteins, where it plays many vital roles, such as helping to read the
genetic code of DNA.
"We know that if there is much zinc in the cell that is not attached to
protein or otherwise encapsulated - so-called 'free zinc' -the cell is
stressed or may be undergoing programmed cell death. This has been observed
in animal models of epilepsy and stroke."
In the past, scientists could only measure the relatively high levels of
zinc in sick cells. The new sensing technology can measure very low free
zinc concentrations in healthy cells.
The technique uses a special protein molecule that has been re-engineered to
report when zinc becomes stuck to it as a change in luminescence that can be
seen in the microscope. This protein (originally found in blood cells) is
very selective, recognizing tiny levels of free zinc even in the presence of
the million-fold higher levels of other metals present in cells, such as
calcium or magnesium.
Because proper zinc levels are so important in health and disease,
scientists have been seeking ways of measuring zinc inside and outside of
cells for more than a decade.
"This is an important discovery," said Sarah B. Tegen, Ph.D., managing
editor of ACS Chemical Biology. "We need to know how the body controls
levels of zinc inside cells. Too much zinc can kill nerve cells. With too
little, nerve cells will not work properly.
"Now we have a metal detector, technology that can measure tiny amounts of
zinc in living cells. Understanding how zinc is stored and released in
different cells throughout the body may help us understand some of the nerve
damage that occurs during a stroke and other nerve injuries."
- Michael Woods
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