the origin of macromolecule ionization by laser irradiation (nobel lecture)

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3860 � 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Angew. Chem. Int. Ed. 2003, 42, 3860

Gentle Mass Spectrometry

The Origin of Macromolecule Ionization by LaserIrradiation (Nobel Lecture)**Koichi Tanaka*

1. Introduction

When I was a student at university, my major field of studywas electrical engineering. I did not specialize in chemistry inmy studies at university, and my knowledge of chemistryoverall was somewhat less than rich. Under those circum-stances, upon entering the Shimadzu Corporation, I appliedmyself wholeheartedly to the study of chemistry to challengeand overcome a barrier in analytical chemistry considered atthat time to be impenetrable. I am, of course, very pleased toreceive the Nobel Prize and further, especially pleased thatthe Prize serves to acknowledge my efforts and results in thefield of analytical chemistry, a field that while rather incon-spicuous to the general population is indeed very importantand useful to the world.

I am employed by the analytical instrument manufacturer,Shimadzu Corporation. I was assigned to a team charged withthe task of designing and building a completely new massspectrometer. The achievement of developing “a soft desorp-tion ionization method for mass spectrometric analysis of

biological macromolecules”, for which I was awarded thisprize, was one aspect of that project. At that period in the1980s, four of my colleagues, whom I will introduce shortly, inaddition to myself, were each in charge of developing a part ofthe instrument. I was responsible for developing the samplepreparation and ionization technologies. Success of theinstrument would not have been assured unless the othertechnologies were suitably provided, even with an excellentionization technology. First, I will briefly describe theprogress of development of the technologies for the othercomponents at that time, other than that of ionization.

Keywords:laser desorption · macromolecules ·mass spectrometry · Nobel lecture

From the Contents

1. Introduction 3861

2. Mass Separation: Time-of-Flight Technology 3862

3. Reflectron Technology 3862

4. Time-Delayed Ion Extraction 3863

5. Ion Detection 3863

6. Ionization Technology 3865

7. Commercialization and Public Announcement 3868

8. Development of MALDI Technology 3869

9. Conclusion 3869

[*] K. TanakaShimadzu Corporation1 Nishinokyo-KuwabarachoNakagyo-ku, Kyoto 604-8511 (Japan)Fax: (+81)75-823-3218E-mail: [email protected]

[**] Copyright4 The Nobel Foundation 2003. We thank the NobelFoundation, Stockholm, for permission to print this lecture.

Nobel LectureAngewandte

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3861Angew. Chem. Int. Ed. 2003, 42, 3861 – 3870 DOI: 10.1002/anie.200300585 � 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

2. Mass Separation: Time-of-Flight Technology

In mass spectrometry, it is necessary to use some methodto separate the generated ions according to mass, and thenperform detection of the ions. One of these methods is calledTime-of-Flight Mass Spectrometry (TOF-MS), whichinvolves separating ions according to mass by measuringtheir respective flight times. Figure 1 provides the simplest

representation of the principle behind TOF-MS. This assumesthat equally charged ions of differing mass,M1,M2, andM3 aregenerated instantly at the same time and starting position.Assume that M1 is the lightest of the ions. The ions aregenerated at an electrical potential V0, and have a potentialenergy of zV0, where z is the charge of the ion andm the massof the ion [Eq. (1)]. If all of the potential energy is converted

zV0 ¼12mv2 ð1Þ

into kinetic energy, the velocity v is expressed by Equa-tion (2), based on the law of conservation of energy. In other

v ¼ffiffiffiffiffiffiffiffiffiffiffiffi2 zV0

m

rð2Þ

words, the lighter ion travels at a higher speed, reaching thedetector first [Eq. (3,4) L= length of drift space, t= flighttime of ion in drift space, t’= flight time of ion in drift spacewith initial kinetic energy e].

t ¼ Lv¼ L

ffiffiffiffiffiffiffiffiffiffiffiffim

2 zV0

rð3Þ

t0 ¼ Lffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi

m2 ðzV0 þ eÞ

rð4Þ

This explanation is based on ideal conditions [Eq. (3)].Since the ions actually possess a distribution of initialvelocities, that is, of the initial kinetic energy e, their arrivaltime t’ at the detector will show some distribution, evenamong ions of equal mass [Eq. (4)]. This situation results indiminished mass resolution.

3. Reflectron Technology

To improve the resolution, it would be best if ions of thesame mass and charge arrive at the detector at the same time,even if their initial kinetic energies are different. Specifically,a device referred to as a “reflectron” (an electrostatic ion“mirror”), first described by Boris Mamyrin et al.[1] in 1973, isused to reflect the ions midway in their flight back towards thedetector. This turning back of the ions has the effect ofadjusting the flight times of the ions in conjunction with theirinitial kinetic energies, to ensure that ions of the same massand charge reach the detector at the same time (Figure 2).

The isochronism of the pendulum is very well known.Stated simply, even if the swing amplitude of the pendulumvaries, the cycle times remain equal provided the cord lengthof the pendulum and the force of gravity stay the same.

Koichi Tanaka, born in 1959 in Toyama,Japan. After completion of his degree inElectrical Engineering at Tohoku Universityhe took a position in the Central ResearchLaboratory of Shimadzu Corporation in1983. His first task was the development ofthe ionization and data acquisition for thetime-of-flight mass spectrometer (TOF-MS)group. In 1985, he established his idea ofsoft laser desorpsion/ionization together withthe hardware of the TOF-MS for observingmacromolecular ions. The results of thegroup were presented at Japanese and then

at international conferences (1987) and in 1989 published in the journalRapid Communications in Mass Spectrometry. He was transferred toKratos Analytical Plc and Shimadzu Research Laboratory (Europe) Ltd. todevelop TOF-MS methods further. In 2002 he shared the Nobel Prize inChemistry with J. B. Fenn and K. Wutrich.

Figure 1. The principles of time-of-flight mass spectrometry.

Figure 2. Improvement of mass resolution by reflectron.

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Applying this principle, an ideal reflectron was developed. Inthis case, the cord length corresponds to the ion mass, theswing amplitude corresponds to the initial kinetic andpotential energy, and the cycle time corresponds to the timeof flight. One method for this reflectron technology (Figure 3)was developed by one of my colleagues at that time, Mr.Yoshikazu Yoshida (Patent number: US4625112, 1986).

4. Time-Delayed Ion Extraction

The principle behind TOF-MS assumes that ions aregenerated instantaneously, that is, in an infinitely shortgeneration time. The time width of a laser pulse is extremelysmall, on the order of a few nanoseconds in the case of the N2

laser. However, when the laser intensity is high enough togreatly exceed the ion-generation threshold, as shown inFigure 4, ions may continue to be generated even after thecompletion of laser irradiation. As a result, in the TOFmodel,

the mass resolution decreases owing to the wider time widthof ion generation.

One of my colleagues at that time, Dr. Tamio Yoshida,succeeded in improving the mass resolution by drawing outthe time from ion generation to ion extraction, as shown inFigure 5. This is accomplished by maintaining equivalentvoltages at the sample plate and the accelerating grid toprevent the ions from being extracted until generation is

complete, and then by creating a potential difference after tDto cause extraction of all the ions at the same time (filed inJapan Patent Office S60035097, 1985). This method is thesame in principle as the time-lag focusing method which wasoriginally designed by William Wiley and Ian McLaren[2] toreduce the effect of initial spatial and kinetic-energy distri-butions, but is now applied specifically to minimize the effectof the prolonged laser-induced ion-generation time.

In addition, there is a heightened possibility that particlesgiven a charge, for example, protons and cations, will collideand react with the normally uncharged sample molecules.Such processes are generally referred to as “chemical ioniza-tion”, as originally described by Burnaby Munson and FrankField.[3] Thus with time-delayed ion extraction the amount ofmolecular ions, such as [M+Na]+ (Figure 6), formed isexpected to increase.

5. Ion Detection

The term detector here refers to the conversion of ionsseparated by the mass-separation mechanism into a flow ofelectrons, in other words, an electrical signal. The maximummass number of ions that had been detected in the early 1980swas in the range of several thousand. In principle, the greaterthe molecular weight (MW) of the ion, the lower the velocityof the ion, and thus the lower the ion-to-electron conversionefficiency, this conversion efficiency could even drop to zero.

The simplest method of raising sensitivity is to acceleratethe ions even further after mass separation occurs (this iscalled “post acceleration”). As shown in Figure 7, the higher

Figure 3. Improvement of mass resolution by ideal reflectron (Patent:US4625112).

Figure 4. Measurement of TOF mass-spectrum with low and high laserpower.

Figure 5. Improvement of mass resolution by time-delayed ion extrac-tion.


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the post-acceleration voltage, the greater the intensity of theions, and further, the higher the mass number, the greater willbe the effect, especially when a high voltage is applied.Another method is the ion-to-electron conversion method. Asshown in Figure 8, the intensity increases using this method aswell.

One of my colleagues at that time, Mr. Yutaka Ido,developed a detector (Figure 9) that obtained the effects ofboth of these methods, which enables sufficiently sensitivedetection even when ions of especially high molecular weightwere generated.

5.1. Measurement Technology5.1.1. Analog-to-Digital Conversion

Even with improved detector sensitivity, it can be assumedthat the intensity of signals arising from macromolecular ionswould be weak. In particular, when performing a single, one-shot measurement using a minute quantity of sample,

successful quantitative analysis may not be possible withouta high enough signal-to-noise ratio. For this reason, aspectrum accumulation circuit is considered to be indispen-sable. To satisfy the demand for an instrument capable ofhigh-speed measurement, our group developed a TOFspectrum measurement accumulation circuit.

One of my colleagues at that time, Mr. Satoshi Akita,developed an analog-to-digital converter (ADC) circuitadopting a “pipeline technique” to achieve the requiredspeedup in measurement. The new ADC circuit provided aprocessing speed of 1 kHz with real-time accumulation of thespectrum at a maximum time resolution of 10 ns and intensityresolution of 24 bit (Figure 10). Moreover, to enable meas-urement of both low-mass high-intensity ions as well as high-mass low-intensity ions, an amplifier that could perform gainswitching within one microsecond was developed andadopted to provide a wider dynamic range.

5.1.2. Time-to-Digital Converter

At that time, ADC circuits had a time resolution of 10 ns.It was our opinion that even this resolution would not beenough. Mr. Yoshikazu Yoshida developed a time-to-digitalconverter (TDC) circuit that could measure up to 255 eventsafter one start signal (Multi-Stop-TDC), which allowed theflight time of the ions to be measured with great accuracy,

Figure 6. Increase in molecular-ion intensity by time-delayed ionextraction.

Figure 7. Ion detection with high-sensitivity by post acceleration;amu=atomic mass unit.

Figure 8. Ion detection with high-sensitivity by ion-to-electron conver-sion; PEG=polyethylene glycol, PPG=polypropylene glycol.

Figure 9. Detection of macromolecule ions by post acceleration andion-to-electron conversion.

K. TanakaReviews



although peak intensity information was sacrificed. As aresult, we were able to measure the time of flight at amaximum time resolution of 1 ns (Figure 10).

All of these crucial developments further emphasize thecertainty that if even one of our group of five were not there,we would not have been able to achieve the measurement ofmacromolecular ions. I am truly happy that the technologieswe developed in the 1980s have been improved through theiruse in various instruments, and that they have played a role inbringing TOF technology into the mainstream ofMS from the1990s.

6. Ionization Technology

Long before the 1980s, there had been investigations intothe use of optical energy, not limited to laser light, to achieveionization of organic compounds.[4] However, for the mostpart, this ionization consisted of stripping electrons fromcompounds in the gas phase.[5] Because this was limited tocompounds that could be vaporized without being decom-posed, very few compounds could be ionized. When a solid-phase organic compound was irradiated with a laser, theorganic compound absorbed the laser light, which providedenough energy for desorption. Further, when the positive andnegative charges of the particle are not in balance, it could bemeasured as an ion. However, in this case, since the laser lightis absorbed directly into the analyte, the molecular bonds maybe broken owing to the increased internal energy. In otherwords, there is an increased risk that measurement wouldoccur in the decomposed state (Figure 11). Because wewanted to measure the undecomposed, intact molecular ion,this was unsatisfactory.

At that time, the molecular weight of compounds thatcould be ionized by laser irradiation was about 1000 Dalton(Da), and ionization of compounds having a molecular weightexceeding 10000 Da was generally considered by chemists atthe time to be impossible. However, not being a specialist inchemistry, I was unaware of the existence of this widely heldbelief.

6.1 Rapid-Heating Technology

In the 1980s, “desorption to gas phase by rapid heating”gained attention through the efforts of several groups that hadobtained some encouraging results. These include FranzRCllgen[6,7] of Germany, Mamoru Ohashi[8] of Japan, andLouis Friedman,[9] Don Hunt,[10] Burnaby Munson,[11] andRobert Cotter[12] of the USA. A simple description of theprinciple is depicted in Figure 12. In short, if a given

compound AB is heated, it is assumed that AB will bereleased to the gas phase as intact AB as well as fragmented Aand B [Eq. (5a,b)]. Respectively applying the well-known

Vaporization : AB KV�!AB ð5aÞ

Decomposition : AB KD�!AþB ð5bÞ

Arrhenius Equation [Eq. (6) where k= rate constant, f= fre-quency factor, E= activation energy, R= gas constant, T=absolute temperature] will give the logarithmic expressionsshown in Equations 7a,b.

k ¼ f exp ð�E=RTÞ ð6Þ

lnKV ¼ lnFV�EV=RT ð7aÞ

lnKD ¼ lnFD�ED=RT ð7bÞ

For compounds that are thermally labile and decomposeeasily, the rate constant for decomposition kD is larger thanthat for vaporization kV at low temperatures. Because theactivation energy for vaporization EV is higher than that fordecompositionED, the slope of the vaporization reaction kV in

Figure 11. Laser desorption/ionization (LDI) from solid or liquidphase.

Figure 12. Temperature dependence of vaporization versus decomposi-tion.[9]

Figure 10. Schematic diagram of the Shimadzu LDI-TOF massspectrometer.


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Figure 12 (lnk versus 1/T) is steeper than that of thedecomposition reaction. If this relationship is always correct,at high temperature, where 1/T is small, vaporization shouldbe favored. In other words, reaching the highest possibletemperature as quickly as possible should provide a highdegree of vaporization.

6.1.1. Use Of Ultrafine Metal Powder

To perform this rapid heating, various heating methodswere devised.[9] However, a high enough temperature couldnot be achieved quickly enough to obtain intact vaporizationof macromolecules, such as proteins. Since the time width of apulse laser itself is between a nanosecond to several micro-seconds, rapid heating would seem possible, that using afocused laser beam would generate energy at high density andhigh speed. However, this would require a medium to enablethe conversion of the irradiating photons into thermal energy.

In Japan at that time in the 1980s, ultrafine metal powder(UFMP) received much attention in the field of metallurgyowing to its usefulness in the efficient production of alloys,and was referred to as “Japanese Powder”. UFMP, as its nameindicates, is an extremely fine metallic powder with particlediameters measuring a few tens of nanometers. The particlediameter of UFMP is about the same as a wavelength, thuswhen compared to bulk metal, there is an increasingpossibility that scattered light could be taken up internally(Figure 13). In other words, light energy could be absorbedmore efficiently. Even visually, UFMP is black in color.

Moreover, the possibility that thermal energy would bedispersed and lost decreases owing to the interparticle spaces.

Mixing UFMP with an organic compound should allowthe laser light to be efficiently absorbed into the UFMP, andto achieve a high UFMP temperature very quickly withoutthe dispersion and loss of heat. This would efficiently achieveheating of the sample in the mixture. It was Mr. YoshikazuYoshida who proposed using UFMP as a matrix (that is, asubstance used to assist ionization; Figure 14; Patent number:JP01731501, filed in 1985, issued in 1993).

There was at that time an interest in using laser desorptionfor the analysis of polymers, such as in the reports by CharlesWilkins et al.[13] of the USA. The MS spectrum shown in theupper part of Figure 15 is obtained when the sample,consisting of a polymer mixture of polyethylene glycols

(PEGs), is irradiated with a laser. The lower spectrum ofFigure 15 shows that of the PEG sample mixed with UFMP.With PEG alone, fragment ion peaks of the PEG moleculeare dominant, and no PEG2000 peaks are observed. On theother hand, not only are there almost no fragment peaksobserved when PEG is mixed with UFMP, the peaks arisingfrom the molecular ion, PEG2000, have become clearlyevident.

With the use of this matrix, the molecular ions from manyorganic compounds that could not be measured previouslycould now be measured by mass spectrometry. However,according to our experimental results, this technique couldnot be applied to compounds with molecular weights in thetens of thousands.

6.1.2. Glycerin Matrix Technology

At that time in the 1980s, the fast atom bombardment(FAB) MS method was widely used to achieve ionization inthermally labile compounds. The FABmethod was developedby Donald Sedgwick and colleagues,[14] and David Surmanand John Vickerman[15] of the UK, and involved acceleratingneutral particles, such as xenon, at high speed so as to collidewith the sample and generate ions. In this method, the solidsample was maintained in a liquid state by using glycerin(glycerol) as a matrix (Figure 16).It is thought that sinceglycerin is a liquid at room temperature, it releases the solidsample from its crystalline state to dissolve in the liquid,

Figure 13. Differences between light absorption by bulk metal andultrafine metal powder.

Figure 14. Molecular-ion desorption by using the UFMP matrix.

Figure 15. Spectra of polyethylene glycol probes with and withoutUFMP matrix.

K. TanakaReviews



thereby assisting ionization. We used glycerin as a matrix, justas it was used in FAB, but because the N2 laser wavelength(337 nm) that we used was only slightly absorbed into theglycerin, no significant effect was seen on the enhancement ofmolecular-ion generation for organic compounds. However,this matrix was useful in improving reproducibility owing toits effectiveness in providing a uniform mixture

6.1.3. UFMP–Glycerin Mixture Technology

Here it can be said that I had come up against a brick wall.Soon after that, while preparing many trial-and-error UFMPsuspensions, changing the organic solvent and concentrationrepeatedly to obtain even the slightest improvement in data, Icommitted a monumental blunder, which was followed by aseries of fortuitous, arbitrary decisions. I was using ordinaryacetone as a UFMP suspension, and one day, by mistake, 1) Iused the glycerin instead of the acetone. Reasoning that itwould be wasteful to discard the expensive UFMP, 2) Idecided to use the “ruined” preparation as the matrixsolution. Because glycerin gradually evaporates in avacuum, I knew it would eventually disappear. However,instead of waiting, 3) I decided to speed up vaporization ofthe glycerine by continuing to irradiate the laser. On top ofthat, because I wanted to see the result as soon as possible,4) I was monitoring the acquisition of the TOF spectrum. Inthis way, only after at least four factors fell into place could Iobserve a phenomenon never before seen.

I think that the sample first measured was vitamin B12. Ihave tried recently to locate the original spectrum, butunfortunately I could not find it. Because vitamin B12 itselfcan absorb laser light with an extremely high degree ofefficiency, up to then, only fragment ions could be measuredwith high sensitivity. However, by using the mixed UFMP–glycerin matrix, at the position where unfragmented ions(molecular ions) should have appeared, peaks which seemedto be noise were observed. No matter how many times Iperformed the measurement, these peaks were present.Molecular ions were observed even after changing thesample, and therefore must be the molecular ion of vita-min B12.

After that, as a result of progressing to higher mass ionswhile optimizing the concentration, laser power, and otherparameters, I was able to measure an ion having a molecularweight of 35 000 Da in 1985 (Figure 17) and in 1987 an ioncluster having a mass number exceeding 100000 Da

(Figure 18). The patent application for this ionizationmethod was submitted in Japan in 1985, and was subsequentlyissued in 1993 (Patent number: JP01769145).

6.2. Why Did The Macromolecule Become Ionized WithoutDecomposing?

Use of UFMP conveniently allows high temperatures tobe reached at high speed. However, when this is mixed with atypical organic compound, it is difficult to achieve sufficientmixing. Even when viewing the mixture in an electron-microscope-generated photograph, the lack of uniformity isobvious (Figure 19, top). When glycerin is added to themixture, however, the uniformity becomes evident (Figure 19,bottom). Moreover, glycerin may also serve to release thesample from its crystalline state. The ability to measuremolecular ions from organic compounds even exceeding amolecular weight of 10000 Da may indeed be due to theseeffects (Figure 20).

Herein I have suggested the principles by which laser-lightirradiation is able to generate huge molecular ions. However,these principles are not necessarily correct because they havenot yet been fully proven scientifically. Even with theknowledge of all the developments in MALDI (matrix-assisted laser desorption/ionization) technology that followedmy discovery, I cannot yet claim to have correctly grasped thetheoretical principles behind all of these phenomena. How-ever, I am an engineer, an engineer employed in a businessenterprise. So even if the principles are unverified, theirapplication takes priority if they are useful and practical.

Figure 16. Molecule desorption/ionization by using a glycerin matrix inFAB-MS.

Figure 17. Molecular-ion measurement of carboxypeptidase A (molecu-lar weight�35k Da).

Figure 18. Molecular cluster-ion measurement of lysozyme (molecularweight=14306 Da).


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7. Commercialization and Public Announcement

If a business organization does not consider that atechnology is basically saleable, development would not beadvanced and there would be no announcement regarding thetechnology outside of the company. If our technology had notbeen made into a product, it would have been buried in-houseand forgotten. For example, similar technology might havebeen developed somewhere else in the world in the 1980s, butif it had not been introduced to the international scientificcommunity, it would not have been further developed tobecome a useful technique worldwide.

Because this basic technology that we developed at theCentral Research Laboratory of Shimadzu Corporation wasto be incorporated into a product, I was transferred to thebusiness division. However, this technology was not madeknown outside the company until it was decided to release the

product. The five members of our group made the firstannouncement outside the company at the Annual Confer-ence of the Japan Mass Spectrometry Society held in Kyoto inMay of 1987 (Oral and poster presentations[16–20] wereconducted in Japanese). The announcement caused somereverberations, however, almost no one believed that thistechnology would become so useful. Of course, we were justpleased and satisfied to confirm that we had made scientificprogress, and further, that we had presented it to the public.

7.1 Technology Transfer to Europe and the USA

In September of 1987, I participated in the Second Japan–China Joint Symposium on Mass Spectrometry that was heldin Takarazuka, Japan, and presented the result for the firsttime in English.[21] At that time in the 1980s, PlasmaDesorption MS (PD-MS) was widely used as a method ofmeasuring macromolecular compounds, such as proteins.[22]

During his presentation there, Professor Robert Cotter statedthat “PD-MS can measure higher masses than laser desorp-tion/ionization (LDI) MS.” Professor Cotter was an authoritywith respect to TOF-MS even at that time, but given my ownrecent results, which I would present the next day, I could notagree with his statement. I apparently indicated to ProfessorCotter that I thought he must be mistaken, and that he shouldlook at my data. Professor Cotter tells me that he was indeedimpressed with the high-mass results. He later saw my posterpresentation and he and Dr. Catherine Fenselau forwardeddetails of our ionization method and copies of the spectra toother researchers in Europe and the USA.

At that time, Dr. Takekiyo Matsuo, an assistant professorat Osaka University who was attending the symposium,strongly recommended that I write a formal paper in English.I reluctantly agreed, and in 1988, our contribution waspublished in Rapid Communications in Mass Spectrometry,[23]

and is now referred to as one of the original sources of theMALDI technique.

7.2. Manufacture of the Instrument and then Termination ofSales

The analytical technology and the instrument became acommercial product. To sell the instrument, I traveled aroundJapan visiting many customers, and actually analyzed morethan two hundred samples. However, the reaction was almostalways, “There is little practical use.” I then looked furtherafield and there was only one potential customer on whom wecould pin our hopes. That was Dr. Terry D. Lee, employed atthe City of Hope's Beckman Research Institute in the USA.The instrument that he bought was in fact the first and onlyinstrument of our commercialized product that was sold, andwe eventually halted development and sales of the instru-ment. Although the instrument could do what no otherinstrument was capable of, it seemed to have little practicaluse. Perhaps, it is fair to say that the sensitivity, accuracy, andresolution required improvement for use in pharmaceuticaland medical diagnostic applications.

Figure 19. Electron microscope images of a) sample and UFMP matrixmixture without glycerin, b) sample and UFMP matrix mixture withglycerin.

Figure 20. Desorption/Ionization of macromolecules by using theUFMP–glycerin mixed matrix.

K. TanakaReviews



8. Development of MALDI Technology

My research and development efforts on MALDI tech-nology remained inactive until 1992 when I was transferredtemporarily to KRATOSAnalytical (a subsidiary company ofShimadzu Corporation from 1989) in Manchester, England.During that period, our technology that had been conveyed toEurope and the USA was steadily being improved upon andreformed through the efforts of Professor Cotter, ProfessorFenselau, and many other researchers throughout the world.Special acknowledgement is warranted for the meritoriousefforts of both Professor Michael Karas and Professor FranzHillenkamp[24–26] of Germany. Were it not for their tremen-dous and continuous efforts and the achievements of thou-sands of other researchers, it is certain that subsequentdevelopment of this technology that has benefited so manypeople around the world would not have occurred.

9. Conclusion

Development of this macromolecule ionization technol-ogy was not accomplished by one genius or gifted person. It isa victory of teamwork, and I believe it is the result of a lot ofhonest activity by many individuals seeking to advance a goodtechnology.

The history of chemistry is long and it is natural that thefield is wide and deep. Because of this, there is a tendency tobelieve that chemistry-related technology is already welldeveloped. It should be mentioned here that I stronglybelieve that building new theories and bringing them to usefulroles in the world requires the total mobilization of knowl-edge in special fields. However, I think it can be said that thetechnique that I discovered and the subsequent technologiesthat originated throughout the world broke through thecommon thinking of chemistry. If I had been caught within thegrasp of this thinking, I would not have been able to make thistype of unique discovery. Even though I cannot claim topossess extraordinary intellectual abilities, and further, myacademic specialization was in a field other than that ofchemistry, there is enough proof that I was able to contributeto the development of chemistry-related technology. With thisin mind, it would give me great pleasure if many peoplearound the world, and especially engineers working in privatebusiness enterprises, would mobilize their courage and holdonto their dreams in the pursuit of scientific innovation forthe benefit of all living beings.

I would like to express my thanks to Mr. Ralph Nesson for histremendous efforts in helping me prepare for my NobelLecture presentation, and for his invaluable insight andpatience in helping me express my thoughts in English. Iwould also like to thank Prof. Robert Cotter, Prof. CatherineFenselau, Dr. Chris Sutton, and Dr. Andrew Bowdler for manystimulating discussions.

Received: February 17, 2003 [A585]

[1] “The Mass- Reflectron, a New Nonmagnetic Time-of-FlightMass Spectrometer with High Resolution”: B. A. Mamyrin, V. I.Karataev, D. V. Shmikk, V. A. Zagulin, Sov. Phys. JETP 1973, 37,45–48.

[2] “Time-of-Flight Mass Spectrometer with Improved Resolution”:W. C. Wiley, I. H. McLaren, Rev. Sci. Instrum. 1955, 26, 1150–1157.

[3] “Chemical Ionization Mass Spectrometry. I. General Introduc-tion”: M. S. B. Munson, F. H. Field, J. Am. Chem. Soc. 1966, 88,2621–2630.

[4] “Photodissociation of Salt Molecules into Ions”: A. Terrenin, B.Popov, Phys. Z. Sowjetunion 1932, 2, 299–318.

[5] “Mass Spectrometry of Aromatic Molecules with Resonance-Enhanced Multiphoton Ionization”: D. M. Lubman, M. N.Kronick, Anal. Chem. 1982, 54, 660–665.

[6] “Ion Formation by [Li]+ Ion Attachment in High ElectricFields”: U. Giessmann, F. W. RCllgen,Org. Mass Spectrom. 1976,11, 1094–1100.

[7] “Field Ion Emitters for Field Desorption of Salts”: F. W.RCllgen, U. Giessmann, H. J. Heinen, S. J. Reddy, Int. J. MassSpectrom. Ion Phys. 1977, 24, 235–238.

[8] “In-beam Electron Impact Mass Spectrometry of AminoSugars”: M. Ohashi, S. Yamada, H. Kudo, N. Nakayama,Biomed. Mass Spectrom. 1978, 5, 578–581.

[9] “Proton Transfer Mass Spectrometry of Peptides. A RapidHeating Technique for Underivatized Peptides ContainingArginine”: R. J. Beuhler, E. Flanigan, L. J. Greene, L. Friedman,J. Am. Chem. Soc. 1974, 96, 3990–3999.

[10] “Chemical Ionization Mass Spectrometry of Salts and ThermallyLabile Organics with Field Desorption Emitters as SolidsProbes”: D. F. Hunt, J. Shabanowitz, F. K. Botz, D. A. Brent,Anal. Chem. 1977, 49, 1160–1163.

[11] “Surface Chemical Ionization Mass Spectrometry”: G. Hansen,B. Munson, Anal. Chem. 1978, 50, 1130–1134.

[12] “The Effects of Heating Rate and Sample Size on the DirectExposure/Chemical Ionization Mass Spectra of Some BiologicalConjugates”: R. J. Cotter, C. Fenselau, Biomed. Mass Spectrom.1979, 6, 287–293.

[13] “High Mass Analysis by Laser Desorption Fourier TransformMass Spectrometry”: C. L. Wilkins, D. A. Weil, C. L. C. Yang,C. F. Ijames, Anal. Chem. 1985, 57, 520–524.

[14] “Fast Atom Bombardment of Solids (F.A.B.): A New Ion Sourcefor Mass Spectrometry”: M. Barber, R. S. Bordori, R. D.Sedgwick, A. N. Tyler, J. Chem. Soc. Chem. Commun. 1981,325–327.

[15] “Fast Atom Bombardment Quadrupole Mass Spectrometry”:D. J. Surman, J. C. Vickerman, J. Chem. Soc. Chem. Commun.1981, 324–325.

[16] “Development of Laser Ionization Time of Flight Mass Spec-trometer I—Curved Electric Field Ion Reflector”: Y. Yoshida,K. Tanaka, Y. Ido, S. Akita, T. Yoshida, Shitsuryo Bunseki RengoToronkai Yoshishu, 1987, 12–13 (in Japanese).

[17] “Development of Laser Ionization Time of Flight Mass Spec-trometer II—High-speed, High-accuracy Measuring Circuit forTOF Spectrum”: S. Akita, K. Tanaka, Y. Ido, Y. Yoshida, T.Yoshida, Shitsuryo Bunseki Rengo Toronkai Yoshishu 1987, 14–15 (in Japanese).

[18] “Development of Laser Ionization Time of Flight Mass Spec-trometer III—Sensitive Ion Detection in High Mass Range”: Y.Ido, K. Tanaka, S. Akita, Y. Yoshida, T. Yoshida, ShitsuryoBunseki Rengo Toronkai Yoshishu, 1987, 20–21 (in Japanese).

[19] “Development of Laser Ionization Time of Flight Mass Spec-trometer IV—Generation of Quasi-Molecular Ions from HighMass Organic Compound”: T. Yoshida, K. Tanaka, Y. Ido, S.Akita, Y. Yoshida Shitsuryo Bunseki Rengo Toronkai Yoshishu,1987, 22–23 (in Japanese).


Chemie



[20] “High Molecular Ion Detection using Laser Ionization TOFMass Spectrometer”: T. Yoshida, K. Tanaka, Y. Ido, S. Akita, Y.Yoshida, Shitsuryo Bunseki Rengo Toronkai Yoshishu, 1987, 30–31 (in Japanese).

[21] “Detection of High Mass Molecules by Laser Desorption Time-of-Flight Mass Spectrometry”: K. Tanaka, Y. Ido, S. Akita, Y.Yoshida, T. Yoshida, Proceedings of the Second Japan-ChinaJoint Symposium on Mass Spectrometry 1987, 185 – 188.

[22] “Plasma Desorption Mass Spectrometry: Coming of Age”: R. J.Cotter, Anal. Chem. 1988, 60, 781A-793A.

[23] “Protein and Polymer Analyses up to m/z 100000 by LaserIonization Time-of-Flight Mass Spectrometry”: K. Tanaka, H.

Waki, Y. Ido, S. Akita, Y. Yoshida, T. Yoshida, Rapid Commun.Mass Spectrom. 1988, 2, 151–153.

[24] “Influence of the Wavelength in High-Irradiance UltravioletLaser DesorptionMass Spectrometry of OrganicMolecules”: M.Karas, D. Bachmann, F. Hillenkamp, Anal. Chem. 1985, 57,2935–2939.

[25] “Laser Desorption Ionization of Proteins withMolecularMassesExceeding 10000 Daltons”: M. Karas, F. Hillenkamp, Anal.Chem. 1988, 60, 2299–2301.

[26] “Ultraviolet-Laser Desorption/Ionization Mass Spectrometry ofFemtomolar Amounts of Large Proteins”: M. Karas, Ingendoh,A. U. Bahr, F. Hillenkamp, Biomed. Environ. Mass Spectrom.1989, 18, 841–843.

K. TanakaReviews



the origin of macromolecule ionization by laser irradiation (nobel lecture)

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