Biopolymer Metal Binding and ETV-ICPMS
1
For the past several years, one of the primary focuses of our research group has been the development of novel ion-exchange systems for the purpose of metal remediation from aqueous systems. Expanding on hints from Mother Nature, we chose to explore the metal chelation abilities of proteins and, in particular, their constituent amino acids. In order to simplify these ion- exchange systems, short-chain homopolymers consisting of repeating monomers of a specified amino acid residue have been used. These systems exhibit many of the characteristics for an ideal ion-exchanger – strong binding; fast, efficient release and structural stability. These biologically- based systems also have the added benefit of being environmentally friendly, unlike many traditional exchange systems which require harsh extraction agents. Developing Fluorescence- based Sensors Resonance energy transfer (RET) can be used to determine various characteristics of metal binding. RET involves the transfer of energy between a fluorescent donor and an acceptor molecule. The efficiency of the energy transfer is dependent on the distance between the molecules, which can be related to their spectroscopic properties. Questions? Email Brianna. [email protected] Anion Binding Anion Binding Residues Residues Amino Acid Amino Acid Cation Binding Residues Cation Binding Residues CH 2 SH Cysteine CH OH Tyrosi ne CH CH 2 C O - O Glutamate Aspartate CH O - C O N CH 2 NH Histidine Lysine (CH 2 ) 4 NH 3 + Other Chelating Other Chelating Residues Residues NH 2 C O CH 2 Asparagine HN Tryptophan CH 2 C NH 2 O CH 2 Glutamin e Arginine (CH 2 ) 3 NH C NH 2 + NH 2 CH 2 H 2 N C COOH H R M + M + M + M + M + M + M + Support The Bonded-Phase Ion-Exchange System Visit us! On the web: http://www.cm.utexas.edu/directory/james_holcombe/ In the Lab: Welch 3.240 and 3.238 Exploring a Combinatorial Approach Questions? Email Carina. [email protected] High throughput screening Library of Oligopeptides U Determine what exclusively binds U Sequence peptide CGGDCCGDGC Synthesize polypeptide( s) and characterize uranium binding + Exposure to mixed metal solution M U Cd Cu High Throughput Screening of Combinatorial Libraries High Throughput Screening Techniques LED - stage illumination Polycapillary optic/ x-ray source Si Li detector Sample Micro-x-ray- fluorescence (MXRF) Fluorescence Microscopy ETV-ICPMS • Bulk screening • Based on fluorescence of bound species • Non-destructive • Single bead screening • Quantitative elemental information • Non-destructive UO 2 2+ in solution Absorption bands: 330- 350nm, 390-440nm Emission bands: 470-570nm with max at 485nm, 510nm, 535nm, and 560nm Moulin, C. et al. Anal. Chem., 1995, 67, 348-353 Bell and Biggers. J. Molec. Spec., 1965, 18, 247-275 1mm Bead in metal solution Metal-bound bead in acid solution Metal solution to be quantified Bind metal Releas e metal • Bulk/single bead screening • Applicable for wide range of metals • Non-destructive TackyDot™ slide to array beads Electrothermal vaporization inductively-coupled plasma mass spectrometry Questions? Email Ram. [email protected] Questions? Email Thomas. [email protected] ETV-ICP-MS for Isobars and Isotopes Questions? Email Adam. [email protected] Creating Chemical-free Remediation Systems Column 3-electrode potentiostat Clean Effluent Stream Metal Recovery Stream valve Reference Electrode E applied Auxiliary Electrode An electrical potential is used to change the binding characteristic s of the column. M n+ M n+ Oxidatio n Reducti on M n+ M n+ M n+ M n+ M n+ Free metal can be bound and released by exposing the ligand to successive reduction and oxidation cycles. Flow Working Electrod es Counter Electrod es Scale up of the electrochemical reactor to practical size requires consideration of materials, geometry, operating conditions, and overall cost. 0 2 4 6 8 10 Tim e,s 0.0E+00 5.0E+06 1.0E+07 1.5E+07 2.0E+07 0 2 4 6 8 10 Tim e,s Intensity 0 2 4 6 8 10 Tim e,s 0.0E+00 2.0E+06 4.0E+06 6.0E+06 8.0E+06 0 2 4 6 8 10 Tim e,s Intensity First Vaporization Stage Second Vaporization Stage One problem with ICP-MS is elements of the same nominal mass (isobaric interference). ETV can be used to separate some problematic elements based on their differing volatilities. Rb and Sr can be separated to remove the isobar at mass 87. -40.0% -30.0% -20.0% -10.0% 0.0% 10.0% 20.0% 30.0% 40.0% 50.0% 60.0% 2050 2100 2150 2200 2250 2300 2350 2400 2450 D etectorPotential Isotope R atio Error M g 1:10 Ti 10:1 Ti 1:1 B a 10:1 B a 1:1 The time of flight design is able to offer excellent isotope ratio precision as a result of simultaneous ion extraction from the plasma. However, difficulties have been encountered with ratio accuracy. Factors that cause this and possible fixes are actively being researched. ICP-MS is the cutting edge technology for atomic spectrometry. It can offer part per trillion detection limits, over 5 orders of magnitude of linear response, and works for almost all elements in the periodic table. It uses an inductively coupled plasma (~8,000 K) as the ionization source. Our ICP-MS uses a time of flight system for mass analysis. Though many labs rely on solution nebulization for sample introduction, this is not always the best technique. It can be problematic for some matrices (e.g. salty solutions, organic solutions, and solids or slurries). An alternative is electrothermal vaporization (ETV). This uses a carbon tube to vaporize the sample before introduction to the ICP-MS. Vaporization temperatures of up to 3,000 o C can be achieved in a controlled manner. It can handle a wide variety of sample types, and generally has higher sample introduction efficiency than nebulizers. To ICP-MS S a m p l e High Throughput Sample Introduction Multi-ETV system for rapid sample introduction, with all of the benefits of a graphite furnace. Coupled with the ICP-TOF, the periodic table can be analyzed every 40 seconds. This is 5 times faster than current techniques! Pneumatic Linear A ctuator A utosam pler R otating Platform C arbon B raids B allJoint C oupler C ells w /Socket Joints 0 5,000,000 10,000,000 15,000,000 20,000,000 25,000,000 30,000,000 35,000,000 Intensity 40 s 40 s 205 Tl
description
High Throughput Screening of Combinatorial Libraries. Exposure to mixed metal solution. U. +. M. Bind metal. Cd. Cu. Library of Oligopeptides. Metal-bound bead in acid solution. Bead in metal solution. Release metal. 1mm. U. - PowerPoint PPT Presentation
Transcript of Biopolymer Metal Binding and ETV-ICPMS
For the past several years, one of the primary focuses of our research group has been the development of novel ion-exchange systems for the purpose of metal remediation from aqueous systems. Expanding on hints from Mother Nature, we chose to explore the metal chelation abilities of proteins and, in particular, their constituent amino acids. In order to simplify these ion-exchange systems, short-chain homopolymers consisting of repeating monomers of a specified amino acid residue have been used. These systems exhibit many of the characteristics for an ideal ion-exchanger – strong binding; fast, efficient release and structural stability. These biologically-based systems also have the added benefit of being environmentally friendly, unlike many traditional exchange systems which require harsh extraction agents.
Developing Fluorescence-based Sensors
Resonance energy transfer (RET) can be used to determine various characteristics of metal binding. RET involves the transfer of energy between a fluorescent donor and an acceptor molecule. The efficiency of the energy transfer is dependent on the distance between the molecules, which can be related to their spectroscopic properties.
Questions? Email [email protected]
Anion Binding Anion Binding ResiduesResidues
Amino AcidAmino Acid Cation Binding ResiduesCation Binding ResiduesCH2
SHCysteine
CH
OHTyrosine
CH
CH2
C
O-
O
Glutamate
Aspartate
CH
O-
C O
N
CH2
NH
Histidine
Lysine
(CH2)4
NH3+
Other Chelating ResiduesOther Chelating Residues
NH2
C O
CH2
AsparagineHN
Tryptophan
CH2
C
NH2
O
CH2
Glutamine
Arginine
(CH2)3
NH
C NH2+
NH2
CH2
H2N C COOH
H
R
M+
M+
M+
M+
M+
M+
M+
Support
The Bonded-Phase
Ion-Exchange System
Visit us! On the web: http://www.cm.utexas.edu/directory/james_holcombe/ In the Lab: Welch 3.240 and 3.238
Exploring a Combinatorial Approach
Questions? Email [email protected]
High throughput screening
Library of Oligopeptides
U
Determine what exclusively binds U
Sequence peptide
CGGDCCGDGCSynthesize
polypeptide(s) and characterize uranium binding
+
Exposure to mixed metal
solutionM
U
Cd Cu
High Throughput Screening of Combinatorial Libraries
High Throughput Screening Techniques
LED - stage illumination
Polycapillary optic/x-ray source
Si Li detector
Sample
Micro-x-ray-fluorescence (MXRF)
Fluorescence Microscopy
ETV-ICPMS
• Bulk screening
• Based on fluorescence of bound species
• Non-destructive
• Single bead screening
• Quantitative elemental information
• Non-destructive
UO22+ in solution
Absorption bands: 330-350nm, 390-440nm
Emission bands: 470-570nm with max at 485nm, 510nm, 535nm,
and 560nmMoulin, C. et al. Anal. Chem., 1995, 67, 348-353
Bell and Biggers. J. Molec. Spec., 1965, 18, 247-275
1mm
Bead in metal solution
Metal-bound bead in acid
solution
Metal solution to be quantified
Bind metal
Release
metal
• Bulk/single bead screening
• Applicable for wide range of metals
• Non-destructive
TackyDot™ slide to array beads
Electrothermal vaporization inductively-coupled plasma
mass spectrometry
Questions? Email [email protected]
Questions? Email [email protected]
ETV-ICP-MS for Isobars and Isotopes
Questions? Email [email protected]
Creating Chemical-free Remediation Systems
Co
lum
n
3-electrode potentiostat
Clean Effluent Stream
Metal Recovery
Stream
valve
Reference Electrode
EappliedAuxiliary Electrode
An electrical potential is used to change the binding characteristics of the column.
Mn+
Mn+
OxidationReduction
Mn+Mn+
Mn+
Mn+
Mn+
Free metal can be bound and released by exposing the ligand to successive reduction and oxidation cycles.
Flow
Working Electrodes
Counter Electrodes
Scale up of the electrochemical reactor to practical size requires consideration of materials, geometry, operating conditions, and overall cost.
0 2 4 6 8 10
Time, s
0.0E+00
5.0E+06
1.0E+07
1.5E+07
2.0E+07
0 2 4 6 8 10
Time, s
Inte
ns
ity
0 2 4 6 8 10
Time, s
0.0E+00
2.0E+06
4.0E+06
6.0E+06
8.0E+06
0 2 4 6 8 10
Time, s
Inte
ns
ity
First Vaporization Stage Second Vaporization Stage
One problem with ICP-MS is elements of the same nominal mass (isobaric interference). ETV can be used to separate some problematic elements based on their differing volatilities. Rb and Sr can be separated to remove the isobar at mass 87.
-40.0%
-30.0%
-20.0%
-10.0%
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
2050 2100 2150 2200 2250 2300 2350 2400 2450
Detector Potential
Iso
top
e R
ati
o E
rro
r
Mg 1:10
Ti 10:1
Ti 1:1
Ba 10:1
Ba 1:1
The time of flight design is able to offer excellent isotope ratio precision as a result of simultaneous ion extraction from the plasma. However, difficulties have been encountered with ratio accuracy. Factors that cause this and possible fixes are actively being researched.
ICP-MS is the cutting edge technology for atomic spectrometry. It can offer part per trillion detection limits, over 5 orders of magnitude of linear response, and works for almost all elements in the periodic table. It uses an inductively coupled plasma (~8,000 K) as the ionization source. Our ICP-MS uses a time of flight system for mass analysis.
Though many labs rely on solution nebulization for sample introduction, this is not always the best technique. It can be problematic for some matrices (e.g. salty solutions, organic solutions, and solids or slurries). An alternative is electrothermal vaporization (ETV). This uses a carbon tube to vaporize the sample before introduction to the ICP-MS. Vaporization temperatures of up to 3,000o C can be achieved in a controlled manner. It can handle a wide variety of sample types, and generally has higher sample introduction efficiency than nebulizers.
To ICP-MS
Sam
ple
High Throughput Sample Introduction
Multi-ETV system for rapid sample introduction, with all of the benefits of a graphite furnace. Coupled with the ICP-TOF, the periodic table can be analyzed every 40 seconds. This is 5 times faster than current techniques!
Pneumatic Linear ActuatorPneumatic Linear Actuator
AutosamplerAutosampler
Rotating PlatformRotating Platform Carbon BraidsCarbon Braids
Ball Joint Coupler
Cells w/ Socket Joints
Ball Joint CouplerBall Joint Coupler
Cells w/ Socket JointsCells w/ Socket Joints
0
5,000,000
10,000,000
15,000,000
20,000,000
25,000,000
30,000,000
35,000,000
Inte
nsi
ty
40 s40 s
205Tl
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