Fundamental knowledge on stable isotopes�
Yochito Chikaraishi and Yuko Takizawa

Application to food authenticity−−+ ×"	×"Protium

C3 plants	

+ ×"	

×"	

×"

Deuterium

Tritium

There is a very very small but certain variation in the ratio of isotopes
among natural samples. Indeed, some of you have a bit larger amount ofheavy isotope than the others, depending on e.g., diet preferences (beefvs. fish vs. vegetable).
Element
1H%
13C

1.11%

13C/12C

0.0111xx

12C 98.890
 1.110

15N 16O 
17O 
18O CO2[Rubisco]C5C3C5CornGrape

99.6350.365

12C

99.760
0.040
0.200

10

PhotosynthateC3 plants
Amino acids

5CO2[Rubisco]

Bulk δ13C (‰)
2C3C4Photosynthate is solo substrate for the biosynthesis of various functionalorganic compounds in biomass.
In general speaking, light isotopes (e.g., 12C, 14N, etc) are preferentiallyreacted, accumulating light one for products, while leaving behind�heavy�oneon the residual pool. As a result, a large variety of δ values are observed in
the organic�compounds within a single organism.

StarchNucleic acids

Photosynthate

0MVA lipids

Photosynthate

Sugarcane

Rice

Chlorophylls

Cellulose

2C3-5LigninMEP lipids

Amino acids
LipidsCarbohydrates

Alkyl lipids

-10Expand 99.9844
 0.0156

14N CO2[PEPC]

Amino acids
LipidsCarbohydrates

2H(D)

13C

C4 plants	
Frequency+ ×"	

Calvin-Benson
cycle

−

There are two types plants with respect to photosynthetic properties: C3 vs.
C4, as Hatch-Slack cycle in C4 efficiently brings CO2 into Calvin-Benson
cycle. This distinct “process” of photosynthesis cases unique 13C/12C balance(δ13C, vs. VPDB) of photosynthate in C3 vs. C4 plants.

δ13C (‰)Isotopes of a given element that have the same number of proton + andelectron − , but different number of neutron.

Isotope physiology

Hatch-Slackcycle

Potential power of stable isotopes

98.89%

Samples A, B, …

For instance, δ13C of many commercial products tell you “source” of them.
As you knows very well, beers are made with barley, so δ13C should be fall ina range of C3 plants (−35 to −25‰). However, some have very positive δ13Cfrom much contamination of C4 products (e.g., sugar).

Chikaraishi (2014) Treatise on Geochemistry 2nd Edition

Biosynthesis of these organic compounds is accomplished by a very complex
network or array of multiple enzymatic reactions. These reaction networks,
empirically those where carbon, hydrogen, and/or nitrogen are added orremoved in specific enzymatic reactions and are separated at branching
points, potentially lead to much or less isotopic fractionation.

, and Z

Gly

RuBP
StarchSuch difference in the weight between isotopes always leads to “differentreactivity” between them, which causes “isotopic fractionation”.
In general, the degree of isotopic fractionation is highly dependent on(1) the isotope ratio in substrate, (2) process, and (3) substrate/productbalance in the reaction.

Cellulose

Calvine
GAP cycle

Sucrose, glucose

A

B

−8‰

5‰

A

B

−3‰

Ser, Gly, Cys
Gly

Brooks et al. (2002)

PheTyr

PEPC20, C40 isoprenoids(e.g., Phytol)

MEP

1×0‰

Abc

B0‰

Aa’

−8‰

Ala

MVAn×Acetyl-CoA

Elongationn-alkyl acyl-ASPn-fatty acids

HCO3–

Resulting in, you can find critical answers for 5W2H in the complex
biogeochemical process in our planet, if you can use “isotope ratios”
very well, smartly, as a master key in your challengings.

Also, 18O/16O balance (δ18O vs. VSMOW) can be useful to identify thegeographical origin of wines. This is based on Isoscape map (i.e,. spatialgraduation) in δ18O cased by dynamic hydrological cycle in the Earth surface.

Unsaturatedfatty acids

To assign & assess“Process”

To use as chemical“Tracer”	 Who	 What	 When	 Where	 When	 Where	 How many	 HowOAA

TCAcycleLys

CO2KGA

Chlorophyllide

ALAGlu

Thr

CA

n-alkanol

North/centralcoastWillametteWest et al. (2007)

SerGlyTTP

CO2n-alkanes

CO2Phytol

Chlorophylls

Arg

Gln

Pro

Chikaraishi (2014) Treatise on Geochemistry 2nd Edition

We would love to contribute to the understanding in-depth the complex
biogeochemical cycle in our planet. To do that, we now are challenging:

SouthcoastTo identify“Sources”

Asp

Met
Ile

Martinelli et al. (2003)

CTP

CO23×PEPB

−1‰

ATP, GTPLeu, Val
C15, C30 isoprenoids(e.g., Sterols)

δ13C (‰)Asp

CO2PyruvateAsna

−5‰
−8‰
−15‰

Formicacid

CO2CO2(3) s/p balanceaLignin

E4P

Fry, 2006

(2) processPGA

CO2PGA

1×

CO20‰

Ser

2×

F6P

Very like beer, some wines too have very positive δ13C as high as C4 plants.

(1) isotope ratio of substrate

Photorespiration

CO2

O2

Illustrated by Prof. Wada

(1) Illumination of “key process” responsible for controlling molecular andstable isotopic compositions of organic compounds in organisms’
physiology,(2) Assessment of “universality & predictable fluctuation” or “homogeneity &heterogeneity” in the isotopic fractionation of the “key process”, and(3) Illustration of “energetic transfer” in biogeochemical cycles.