team d mohammed zuned desai areio barzan hashemi koji hirota michael james wong

Team DMohammed Zuned DesaiAreio Barzan Hashemi

Koji HirotaMichael James Wong

Magnetic TweezersExerts magnetic forces to

determine mechanical properties of molecules, proteins, chemical bonds

AdvantagesThe magnet configurations are

relatively easy to assembleMagnetic forces are orthogonal to

biological interactionsOffer the prospect for massively

parallel single-molecule measurements

Figure 1: Illustration of Magnetic Tweezers, adapted from http://www.nature.com/nature/journal/v421/n6921/images/nature01405-f2.0.jpg

layer modified with protein

force

How do Magnetic Tweezers Work?Magnet(s)

Stage

PDMS Wells Containing Sample

10x Objective Lens

CCD Camera

Light Source

Mirror

Figure 2: Diagram of setup of magnetic tweezersFigure 3: Animation of how magnetic tweezers work

layer modified with ligands

How Magnetic Tweezers Work?What do these forces depend on?

The force on the paramagnetic beads depend on the magnetic moment and the magnetic field gradient ( )

To achieve higher forces we either increase or m

Force Calculations:

BmFM

BB

Fd

Fg

FM

0.2 mm0.2 mm0.2 mm

B = 800GB = 700GB = 620GB = 560G

Magnet

Sample attached to paramagnetic beads

Magnetic Field Gradient• What do we mean by magnetic

field gradient ?• Want to achieve a high

gradient• For the same distance we

want a constant change in gradient

Figure 4: Diagram demonstrating the definition of homogeneous gradient

ObjectivesMain goal is to focus on

attaining forces with the Magnetic Tweezers for single-molecule measurements (e.g. 5 – 100 pN):Design producing the

highest gradient Achieving force higher

than 1.5pN (previous group)

Calibrating the selected design

Figure 5 and 6: Setup of last years senior design group taken at different angles.

High Magnetic GradientTo maximize the magnetic gradient

Build the stronger magnet(s) with materialsGeometry shape and position

Using FEMM (Finite Element Method Magnetics)

Figure 8: Double Magnet FEMM Design Figure 9: Single Magnet FEMM Design

Single Magnet DesignUsing FEMM simulation program

Choose the materialsDesign the core including

length, diameter and shapeOutcome

CORESteel127mm (5 in.) core length 6.35mm (0.25 in.) core diameterFlat Shape

COIL30 Gauge Copper wire2500 coil turns91.44mm (3.6 in.) coil length15.49mm (0.61 in.) coil diameter

Figure 11: Picture of the magnet (coil and core)

Double Magnets Design

Figure 10: Drawing of final double magnet design

• From the literature research and FEMM simulation, this design of

double magnets should exert higher magnetic gradient

Magnetic Tweezers Setup Single Magnet

Up to 5.9 pN

Double magnetsUp to 3.5 pN

Figure 12: Close up picture of single magnet design Figure 13: Close up picture of double magnet design

Inverse relationship of strength of magnetic field over distance

Measuring Magnetic Gradient by Gaussmeter

Measure magnetic gradient over distance

Graphs to be linearMagnetic gradient is

decreasing at a constant rate

Compare magnetic gradient within working distance (2mm) Single Magnet: 148.43

G/mm Double Magnet: 120.56

G/mm

Figure 14 and 15: Comparison of the gradient results for the single magnet and double magnet

Magnet

Stage

1mm Capillary Tube With Paramagnetic Beads

10x Objective Lens

CCD Camera

Light Source

Magnets

Stage


10x Objective Lens

CCD Camera

Light Source

Calibration Process: Setup

Figure 16: Calibration setup for the single magnet Figure 17: Calibration setup for the double magnet

Actual Setup

Power Supply

Adjustable Stage

Magnet(s)

CCD Camera

10x Objective Lens

LED Light Source

Sample Stage withCapillary Tube

Figure 7: Picture of the setup of our final design

Calibration Process1) Zero apparatus

Have the tip of the magnet close to the capillary tube

2)Inject beads into the capillary tube

3)Turn on the power source

4) Note time it takes for the bead to travel 0.5mm

Magnet

Stage


10x Objective Lens

CCD Camera

Light Source

Calibrating Magnetic TweezersForce calculations using Stoke’s

drag equation:Calibrate:

Distance between the core of the electromagnet and paramagnetic beads

Gravitational Force ~ 0.3 pNExample:

Time it takes bead to move vertically 0.5mm = 9.4s

Velocity of bead (v) = 0.054 mm/s Fluid’s viscosity (u)= 3.63 mPa s (40% Glycerol

Solution) Radius of bead (r) = 1.5 um Net Force (Fm) = 5.91 pN

rFd 6

15

gdM FFF

F mB

force

Fd Fg

FM

Figure 18: Animation of forces acting on the bead

Sample Calibration Video

0.25mm

0.5mm

0.75mm

1mm

0mm

Video 1 : Sample video of beads moving for the calibration process

Calibration Results 3V ResultsSingle Magnet CalibrationForce at 1mm: 1.02pNForce at 2mm: 0.98pN

Double Magnet CalibrationForce at 1mm: 0.76pNForce at 2mm: 0.73pN

6V ResultsSingle Magnet CalibrationForce at 1mm: 2.23pNForce at 2mm: 1.85pN


Figure 19 and 20: Caparison of the forces the single and double magnet could achieve using 3V and 6V

Calibration Results

12V ResultsSingle Magnet CalibrationForce at 1mm: 5.91pNForce at 2mm: 4.84pN


We are mainly concerned about the 12V measurementsThe results show that the single magnet can achieve higher forces than the double magnet

Figure 21: Caparison of the forces the single and double magnet could achieve using 12V

ConclusionWe accomplished our objectives:

1) We were able to design and build a pair of magnetic tweezers that can achieve over 1.5pNSingle magnet magnetic tweezers can achieve

3.94times more force than old designDouble magnet magnetic tweezers can achieve

2.35times more force than old design2) Successfully able to calibrate both magnetic

setups

Future Workm = magnetic moment in a superparamagnetic bead B = magnetic field in Tesla

I = amperesn = turns per meterK = permeability = magnetic constant

Permeability of steel = 100Permeability of Mu Metal = 20,000

F mB

0

B K0nI

Future Work

Mu Metal Nickel-iron alloy

Permeability Ability to support magnetism 200 times than that of steel

Heat treatment Reduces amount of oxygen in metal Gains back permeability that was lost

Future WorkHeat Conduction

Thermoelectric Cooling Peltier Cells

Liquid Cooling System Water Blocks

Future WorkStage

Holds PDMS wells and tubeRepeatable parametersDetachable

Fitted to optics table or microscope if needed

AcknowledgmentsDr. Valentine VullevDr. Sharad GuptaDr. Hyle ParkDr. Jerome SchultzGokul UpadhyayulaHong Xu

References 1) Neuman, Keri C, and Nagy, Attila. “Single-molecule force spectroscopy:

optical tweezers, magnetic tweezers and atomic force microscopy.” Nature Publishing Group Vol. 5, NO. 6. June 2008.

2) Danilowicz, Claudia, Greefield, Derek and Prentiss, Mara. “Dissociation of Ligand-Receptor Complexes Using Magnetic Tweezers.” Analytical Chemistry Vol. 77, No. 10. 15 May. 2005.

3) Humphries; David E., Hong; Seok-Cheol, Cozzarelli; Linda A., Pollard; Martin J., Cozzarelli; Nicholas R. “Hybrid magnet devices fro molecule manipulation and small scale high gradient-field applications”. United States Patent and Trademark Office, An Agency of The United States Department of Commerce. <http://patft.uspto.gov>. January 6, 2009.

4) Ibrahim, George; Lu, Jyann-Tyng; Peterson, Katie; Vu, Andrew; Gupta, Dr. Sharad; Vullev, Dr. Valentine. “Magnetic Tweezers for Measuring Forces.” University of California Riverside. Bioengineering Senior Design June 2009.

5) Startracks Medical, “Serves Business, Education, Government and Medical Facilities Worldside.” American Solution. Startracks.org, Inc. Copyright 2003. <http://images.google.com/imgres?imgurl=http://www.startracksmedical.com/supplies/invertedmicroscope.jpg&imgrefurl=http://www.startracksmedical.com/supplies.html&usg=__butCY2zWJa7nAkwkjiPxX_mFy0=&h=450&w=450&sz=24&hl=en&start=2&um=1&tbnid=XH6gnQuJLS7bRM:&tbnh=127&tbnw=127&prev=/images%3Fq%3Dinverted%2Bmicroscope%26hl%3Den%26sa%3DN%26um%3D1>

6) Janshoff A, Neitzert M, Oberdorfer Y, Fuchs H. Force spectroscopy of molecular systems-single molecule spectroscopy of polymers and biomolecules. Angew Chem Int Ed 2000;39:3212-3237.

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