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Accelerated Chlorophyll Reaction in Microdroplets to Reveal Secret of Photosynthesis

  • 조회. 604
  • 등록일. 2017.02.13
  • 작성자. Administrator

Accelerated Chlorophyll Reaction in Microdroplets to

Reveal Secret of Photosynthesis 






- The research team of DGIST’s fellow Hong Gil Nam, discovered

the natural control of chlorophyll activity 



- New mechanisms to protect photosynthesis organisms and control

its efficiency are expected 



 














Figure 1. When the chlorophyll encounters an acid, a demetallation reaction occurs in which the magnesium metal ions of the chlorophyll are converted into hydrogen ions. This reaction occurs in many different types of chlorophyll, and the optical, electrical and chemical properties of the chlorophyll are changed by this reaction.






DGIST announced that the research team of the fellow Hong Gil Nam (Head of Center for Aging Research,

Institute for Basic Science) at the Department of New Biology
and the

research team of Professor Richard N. Zare of Stanford University have found in

their joint research that chlorophyll demetallation is naturally accelerated a thousand times faster in microdroplets without any help of enzymes.






Chlorophyll is a green pigment molecule found in photosynthetic

organisms and plays a key role in the first step of photosynthesis, which

absorbs light and converts it into chemical energy.






In recent years, several research groups have reported the

phenomenon of accelerated chlorophyll reactions in microdroplets. Mostly,

evaporation of the solvent or low voltage was pointed as the main causes of the

acceleration. However, this study conducted experiments to verify various

hypotheses without accepting existing assertions and found that the limitation

effect of physical space of micro-sized droplets is the cause of accelerated

reaction. 






The team paid attention to the chemical reaction of chlorophyll in

order to reveal the control secret of the absorption and transfer of solar energy.

In the acidic condition, chlorophyll demetallation reaction occurs in which the

magnesium ions at the center of the chlorophyll are replaced with the hydrogen

ions. So far, the importance of this reaction in photosynthesis has been

overlooked as the reaction rate of the demetallation in bulk solution was very

slow compared to the absorption and transfer rate of solar energy in many

experiments.






The research team has found that the chlorophyll demetallation

reaction gets a thousand times faster in microdroplets by applying the method

to measure the reaction rate of biochemicals in microdroplets which was

developed in 2015. This suggests the possibility of a new mechanism of

photosynthesis control by rediscovering the importance of chlorophyll reaction.






In living organisms, a variety of biochemical reactions take place

in physically confined spaces. Photosynthesis also occurs in the organelles,

the chloroplasts of plants, and the smaller structures called "grana" in

chloroplasts absorb light. The team observed the reaction kinetics of

biochemical reactions by creating microdroplets to look at the reaction of

chlorophyll under the similar environment to the actual physical space of a

plant.






The research team collided water droplets containing chlorophyll

with water droplets containing hydrochloric acid at high speed to make micro-sized

fused droplets. Then, they recorded kinetics of acid-induced chlorophyll

demetallation by controlling the travelling distance of the fused

microdroplets.

















Figure 2. Experimental setup for chlorophyll

demetallation kinetics 
using microdroplet fusion mass spectrometry.






As a result, it was found that chlorophyll demetallation occurs at a

time of several tens of microseconds, which is about a thousand times faster

than that measured in bulk solution. This result is presumed to be due to the

limitation of the physical space of microdroplets as well as the surface effect

of droplets themselves.











DGIST’s Hong Gil Nam said "When chlorophyll is oxidized, it

loses its photosynthesis function. However, the demetallation reaction can

protect the chlorophyll as it prevents the oxidation of chlorophyll." He

added "This study suggests that the demetallation reaction of chlorophyll

can be a new mechanism which can protect photosynthetic organisms or control

photosynthetic efficiency and that the reaction can be fast enough without any enzymatic

action unlike conventional thinking."



 



The team expects that the discovery of a new mechanism of

photosynthesis would bring better understanding of the operation of

photosynthesis and contribute to further studies to find elements and methods

for more efficient photosynthesis.






Meanwhile, this study was published on January 1, 2017 in the online

edition of
Quarterly Reviews of

Biophysics
, an international academic journal in the field of biophysics.









Journal

Reference



Jae

Kyoo Lee, Hong Gil Nam and Richat N. Zare, “Microdroplet Fusion Mass

Spectrometry : Accelerated Kinetics of Acid-Induced Chlorophyll Demetallaton”

Quarterly Reviews of Biophysics, 2017.






Abstract



Kinetics of acid-induced chlorophyll

demetallation was recorded in microdroplets by fusing a stream of microdroplets

containing 
40 μM chlorophyll a or b dissolved in

methanol with a stream of aqueous microdroplets containing 35 mM hydrochloric

acid (pH = 1·46). 
The kinetics of the demetallation of

chlorophyll in the fused microdroplets (14 ± 6 μm diameter; 84 ± 18 m s−1

velocity) was recorded by 
controlling the traveling distance of the

fused microdroplets between the fusion region and the inlet of a mass

spectrometer. The rate of 
acid-induced chlorophyll demetallation was

about 960 ± 120 times faster in the charged microdroplets compared with that

reported in 
bulk solution. If no voltage was applied to

the sprayed microdroplets, then the acceleration factor was about 580 ± 90,

suggesting that the 
applied voltage is not a major factor

determining the acceleration. Chlorophyll a was more rapidly demetallated than

chlorophyll b by a factor 
of 26 in bulk solution and 5 in charged microdroplets. The demetallation kinetics was second

order in the H+ concentration, but the acceleration 
factor of microdroplets compared with bulk

solution appeared to be unchanged in going from pH = 1·3 to 7·0. The

water:methanol 
ratio of the fused microdroplets was varied

from 7:3 to 3:7 causing an increase in the reaction rate of chlorophyll a

demetallation by 20%. This 
observation demonstrates that the solvent

composition, which has different evaporation rates, does not significantly

affect the acceleration. We 
believe that a major portion of the

acceleration can be attributed to confinement effects involving surface

reactions rather than either to evaporation 
of solvents or to the introduction of

charges to the microdroplets.






[DGIST Research News in Media] 



 [Phys.org] Accelerated chlorophyll reaction in microdroplets to reveal secret of photosynthesis



● [EurekAlert!] Accelerated chlorophyll reaction in microdroplets to reveal secret of photosynthesis



[EnvironmentGuru.com] Accelerated chlorophyll reaction in microdroplets to reveal secret of photosynthesis