* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Post Info
TOPIC: Ingredients for life


L

Posts: 131433
Date:
Left-handed amino acids
Permalink  
 


An honours class on chemical evolution and the origin of life led to research that might help to better explain how a molecular quirk developed in all life on Earth.
The research suggests that the light emitted by the remnants of an exploded star more than 4.5 billion years ago could have produced the quirk during organic chemical evolution that took place before the origin of life. ASU chemists John R. Cronin and Sandra Pizzarello published their findings in the Feb. 14, 1997 issue of the journal Science.
Scientists have known for a long time that many compounds in living things exist in mirror-image forms.
One-handed compounds are needed because without them, large biological molecules, like proteins, would be unable to form reproducible structures. When scientists make the same compounds in the laboratory, half the molecules come up left-handed, half right-handed. But in Earth organisms, amino acids, which are the building blocks of life, are all left-handed.
Two major theories propose answers. According to one theory, there was some sort of influence acting on chemical evolution before the origin of life that either promoted the development of left-handed amino acids, or the breakdown of right-handed amino acids.
The other theory says that molecular handedness developed as a matter of biological evolution, after the origin of life.

Read more

Ed ~ Other studies have shown that polarized radiation from a young Sun created the imbalance and development of left-handed amino acids.

__________________


L

Posts: 131433
Date:
Ingredients for life
Permalink  
 


George W. Cooper from NASA-Ames Research Centre will talk about the origins of life on Earth when he delivers the first Barringer Lecture for the spring 2008 semester. The lecture will be held at 7 p.m. Monday, Feb. 11, in the Space Centre Theatre, Room 201 of the old University Museum building. Admission is free and open to all members of the university community and the public.
Carbonaceous meteorites and comets contain a diverse suite of carbon compounds. Meteorites have been delivering these compounds to Earth throughout the life of the solar system and therefore were likely to have played an important role in the origin and/or evolution of life.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

Did Life Evolve in Ice?
One morning in late 1997, Stanley Miller lifted a glass vial from a cold, bubbling vat. For 25 years he had tended the vial as though it were an exotic orchid, checking it daily, adding a few pellets of dry ice as needed to keep it at 108 degrees Fahrenheit. He had told hardly a soul about it. Now he set the frozen time capsule out to thaw, ending the experiment that had lasted more than one-third of his 68 years.
Miller had filled the vial in 1972 with a mixture of ammonia and cyanide, chemicals that scientists believe existed on early Earth and may have contributed to the rise of life. He had then cooled the mix to the temperature of Jupiters icy moon Europatoo cold, most scientists had assumed, for much of anything to happen. Miller disagreed. Examining the vial in his laboratory at the University of California at San Diego, he was about to see who was right.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 



__________________


L

Posts: 131433
Date:
Permalink  
 

Life on Earth began on a radioactive beach, a scientist claimed today.
The sifting and collection of radioactive material by powerful tides could have generated the complex molecules that led to the evolution of carbon-based life forms - including plants, animals and humans.
While radiation may seem an unlikely candidate to kick-start life because it breaks chemical bonds and splits large molecules, it also crucially provides chemical energy needed to generate some of the basic building blocks of life.
Zachary Adam, an astrobiologist at the University of Washington in Seattle, has suggested the collection of radioactive material on a beach as a new theory for the origins of life - to be added to the existing long and varied list of hypotheses.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

Astronomers from Arecibo Observatory radio telescope in Arecibo, Puerto Rico, have detected for the first time the molecules methanimine and hydrogen cyanide -- two ingredients that build life-forming amino acids -- in a galaxy some 250 million light years away.
When combined with water, the molecules form glycene, the simplest amino acid and a building block of life on Earth.
The astronomy team, led by Arecibo astronomer Christopher Salter, announced the discovery Jan. 11 in a poster presented at the American Astronomical Society meeting in Austin, Texas.
The Arecibo astronomers focused on the distant galaxy Arp 220, an ultra-luminous starburst galaxy, because it forms new stars at a very high rate. They used the 305-meter, or 1,000-foot diameter, Arecibo radio telescope, the world's largest and most sensitive, to observe the galaxy at different frequencies. The observations, made in April 2007, were the first use of the 800 megahertz wide-band mode of the telescope's main spectrometer.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

The universe might have been hospitable for life 500 million years earlier than we thought, according to researchers at the University of Texas in Austin.
The earliest galaxies probably initially consisted only of dark matter haloes and primordial hydrogen and helium gas. Massive amounts of UV radiation at the time should in theory have suppressed the formation of the very first stars. This meant many of life's building blocks, such as carbon, oxygen, silicon and iron, could not be dispersed via stellar supernova explosions until later

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

Pizza hypothesis
Life may have begun in the protected spaces inside of layers of the mineral mica, in ancient oceans, according to a new hypothesis by a UCSB research scientist. The hypothesis proposes that the narrow confined spaces between the thin layers of mica could have provided exactly the right conditions for the rise of the first biomoleculeseffectively creating cells without membranes.
The hypothesis was developed by Helen Hansma, a research scientist with the University of California, Santa Barbara and a program director at the National Science Foundation. Hansma presented her findings at a press briefing this morning, at the annual meeting of the American Society for Cell Biology in Washington, D.C.

Read more

__________________


L

Posts: 131433
Date:
Liquid Crystal Life
Permalink  
 


A team led by the University of Colorado at Boulder and the University of Milan has discovered some unexpected forms of liquid crystals of ultrashort DNA molecules immersed in water, providing a new scenario for a key step in the emergence of life on Earth.
CU-Boulder physics Professor Noel Clark said the team found that surprisingly short segments of DNA, life's molecular carrier of genetic information, could assemble into several distinct liquid crystal phases that "self-orient" parallel to one another and stack into columns when placed in a water solution. Life is widely believed to have emerged as segments of DNA- or RNA-like molecules in a prebiotic "soup" solution of ancient organic molecules.

Read more

__________________


L

Posts: 131433
Date:
RE: Ingredients for life
Permalink  
 


A team led by the University of Colorado at Boulder and the University of Milan has discovered some unexpected forms of liquid crystals of ultra-short DNA molecules immersed in water, providing a new scenario for a key step in the emergence of life on Earth.
CU-Boulder physics Professor Noel Clark said the team found that surprisingly short segments of DNA, lifes molecular carrier of genetic information, could assemble into several distinct liquid crystal phases that self-orient parallel to one another and stack into columns when placed in a water solution. Life is widely believed to have emerged as segments of DNA- or RNA-like molecules in a prebiotic soup solution of ancient organic molecules.
A paper on the subject was published in the 23 November issue of Science. The paper was authored by Clark, Michi Nakata and Christopher Jones from CU-Boulder, Giuliano Zanchetta and Tommaso Bellini of the University of Milan, Brandon Chapman and Ronald Pindak of Brookhaven National Laboratory and Julie Cross of Argonne National Laboratory. Nakata died in September 2006.

Since the formation of molecular chains as uniform as DNA by random chemistry is essentially impossible, Clark said, scientists have been seeking effective ways for simple molecules to spontaneously self-select, chain-up and self-replicate. The new study shows that in a mixture of tiny fragments of DNA, those molecules capable of forming liquid crystals selectively condense into droplets in which conditions are favourable for them to be chemically linked into longer molecules with enhanced liquid crystal-forming tendencies, he said.

"We found that even tiny fragments of double helix DNA can spontaneously self-assemble into columns that contain many molecules. Our vision is that from the collection of ancient molecules, short RNA pieces or some structurally related precursor emerged as the molecular fragments most capable of condensing into liquid crystal droplets, selectively developing into long molecules" - Noel Clark.

Liquid crystals organic materials related to soap that exhibit both solid and liquid properties are commonly used for information displays in computers, flat-panel televisions, cell phones, calculators and watches. Most liquid crystal phase molecules are rod-shaped and have the ability to spontaneously form large domains of a common orientation, which makes them particularly sensitive to stimuli like changes in temperature or applied voltage.
RNA and DNA are chain-like polymers with side groups known as nucleotides, or bases, that selectively adhere only to specific bases on a second chain. Matching, or complementary base sequences enable the chains to pair up and form the widely recognised double helix structure. Genetic information is encoded in sequences of thousands to millions of bases along the chains, which can be microns to millimetres in length.
Such DNA polynucleotides had previously been shown to organise into liquid crystal phases in which the chains spontaneously oriented parallel to each other, he said. Researchers understand the liquid crystal organisation to be a result of DNAs elongated molecular shape, making parallel alignment easier, much like spaghetti thrown in a box and shaken would be prone to line up in parallel, Clark said.
The CU-Boulder and University of Milan team began a series of experiments to see how short the DNA segments could be and still show liquid crystal ordering, said Clark. The team found that even a DNA segment as short as six bases, when paired with a complementary segment that together measured just two nanometers long and two nanometers in diameter, could still assemble itself into the liquid crystal phases, in spite of having almost no elongation in shape.
Structural analysis of the liquid crystal phases showed that they appeared because such short DNA duplex pairs were able to stick together end-to-end, forming rod-shaped aggregates that could then behave like much longer segments of DNA. The sticking was a result of small, oily patches found on the ends of the short DNA segments that help them adhere to each other in a reversible way much like magnetic buttons as they expelled water in between them, Clark said.
A key characterisation technique employed was X-ray microbeam diffraction combined with in-situ optical microscopy, carried out with researchers from Argonne and Brookhaven National Laboratories. The team using a machine called the Argonne Advanced Photon Source synchrotron that enabled probing of the nano DNA molecular organisation in single liquid crystal orientation domains only a few microns in size. The experiments provided direct evidence for the columnar stacking of the nano DNA pieces in a fluid liquid crystal phase.

"The key observation with respect to early life is that this aggregation of nano DNA strands is possible only if they form duplexes. In a sample of chains in which the bases dont match and the chains cant form helical duplexes, we did not observe liquid crystal ordering" - Noel Clark.

Subsequent tests by the team involved mixed solutions of complementary and non-complementary DNA segments, said Clark. The results indicated that essentially all of the complementary DNA bits condensed out in the form of liquid crystal droplets, physically separating them from the non-complementary DNA segments.

"We found this to be a remarkable result. It means that small molecules with the ability to pair up the right way can seek each other out and collect together into drops that are internally self-organised to facilitate the growth of larger pairable molecules. In essence, the liquid crystal phase condensation selects the appropriate molecular components, and with the right chemistry would evolve larger molecules tuned to stabilise the liquid crystal phase. If this is correct, the linear polymer shape of DNA itself is a vestige of formation by liquid crystal order" - Noel Clark .

Read more

__________________
«First  <  19 10 11 12 13  >  Last»  | Page of 13  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard