An ESR Study of Amino Acid and Protein Free Radicals in Solution - PART II. Identification of Amino Acid Free Radicals Produced by Ti-$H_2O_2$ Flow System

홍순주,Hong, Sun-Joo,Piette, L.H. 생화학분자생물학회 1971 한국생화학회지 Vol.4 No.1

Ti-$H_2O_2$ flow-mixing system에서 만들어진 아미노산 자유기를 ESR법으로 동정하고 이 결과와 방사선에 의해 생성된 경우와를 비교 검투했다. 이 system으로 만들어진 각 아미노산의 자유기는 반드시 한 가지 만은 아님이 밝혀졌는데 이 실험에서 얻은 각 ESR 스펙트럼은 glycine에서는 주로 $\dot{C}H({NH_3}^+)COO^-$, DL-$\alpha$-alanine에서는 주로 $\dot{C}H_2CH({NH_3}^+)COO^-$, $\beta$-alanine에서는 주로 $CH_2({NH_3}^+)\dot{C}H{COO_3}^-$, DL-valine에서는 $(CH_3)_2\dot{C}CH({NH_3}^+)COO^-$와 거의 동율로 $\dot{C}H_2CH(CH_3)\dot{C}H({NH_}^+)COO^-$, DL-serine에서는 $\dot{C}H(OH)CH({NH_3}^+)COO^-$, L-cysteine, cystine 및 gIutathione에서는 주로 $RCH_2\dot{S}$, DL-threonine에서는 주로 $CH_3\dot{C}(OH)CH({NH_3}^+)COO^-$, DL-leucine에서는 주로 $\dot{C}H_2CH(CH_3)CH_2CH({NH_3}^+)COO^-$, DL-methionine에서는 주로 $CH_2SCH_2\dot{C}HCH({NH_3}^+)COO^-$, 그리고 L(+)arginine에서는 주로 $HN=C(NH_2)NHCH_2\dot{C}HCH_2CH({NH_3}^+)COO^-$의 생성을 나타내고 있음을 확인했다. 결국, 방사선에 의한 아미노산 자유거의 생성은 알파위치에서 수소원자를 떼어냄으로서 생성되는데 반해 이 system에서는 일차적으로 생성된 친(親)전자성인 수산기가 아미노산 분자의 guanidium 기, carboxyl 기 또는 proton이 더해진 amino 기에서 가급적 먼 위치에서 수소원자를 떼어 냄으로써 생성됨을 알았다. 본실험에서 수산기수소에 의한 splitting이 선명하게 들어난 것은 특기할 일이며 이 실험에서 다룬 아미노산 중에서 L-cysteine과 DL-methionine을 제외한 모든 아미노산의 경우에는 그의 자유기 생성이 염산에 의해 저해를 받은 반면, 황산은 염산의 경우와 정반대의 영향을 끼친다는 사실을 알았다. Free radicals generated by exposing amino acids to Ti-$H_2O_2$ flow mixing system were identified by electron spin resonance spectroscopy. Hydrogen atom abstraction by the reactive primary radical, having electrophilic character, was found to occur at the carbon atom furthest from the guanidium, carboxyl and protonated amino group, and sulfur atom. The main radical species from DL-leucine, DL-methionine. and L(+)arginine were assigned to be $\dot{C}H_2CH(CH_3)CH_2CH({NH_3}^+)COO^-$, $\dot{C}H_3SCH_2\dot{C}HCH({NH_3}^+)COO^-$ and $NH=C(NH_2)NHCH_2\dot{C}HCH_2CH({NH_3}^+)COO^-$ respectively. The splitting for the hydroxyl hydrogen was also clearly observed in the system for DL-serine free radical, $\dot{C}H(OH)CH({NH_3}^+)COO^-$. Generally, HCl appeared to interfere with the free radical production for most of the amino acids investigatd except L-cysteine and DL-methionine in contrast with $H_2SO_4$ which enhances most signals but not with the latter.

용액에서의 아미노산 및 단백질 자유기에 관한 ESR 연구 제 2 보 Ti - H2O2 flow system 으로 만든 아미노산 자유기의 동정

홍순주,L . H . Piette ( Sun Joo Hong ) 생화학분자생물학회 1971 BMB Reports Vol.4 No.1

Free radicals generated by exposing amino acids to Ti-H₂O₂ flow mixing system were identified by electron spin resonance spectroscopy. Hydrogen atom abstraction by the reactive primary radical, having electrophilic character, was found to occur at the carbon atom furthest from the guanidium, carboxyl and protonated amino group, and sulfur atom. The main radical species from DL-leucine, DL-methionine and L (+) arginine were assigned to be CH₂CH (CH₃) CH₂CH (NH₃^+)COO^-, CH₃SCH₂CHCH(NH₃^+)COO^- and NH=C(NH₂)NHCH₂CHCH₂CH(NH₃^+) COO^- respectively. The splitting for the hydroxyl hydrogen was also clearly observed in the system for DL-serine free radical, CH (OH) CH (NH₃^+) COO^-. Generally, HCl appeared to interfere with the free radical production for most of the amino acids investigated except L-cysteine and DL-methionine in contrast with H₂SO, which enhances most signals but not with the latter.

An ESR Study of Amino Acid and Protein Free Radicals in Solution. Part IV. An ESR study of Gamma-Irradiated Amino Acids in Frozen Aqueous Solutions.

Sun-Joo Hong,D. E. Holmes,L. H. Piette. Korean Chemical Society 1971 대한화학회지 Vol.15 No.5

An ESR study has been made on free radicals produced in frozen aqueous solutions (ices) of glycine, DL-${\alpha}$-alanine, DL-serine, L-cysteine, DL-leucine and DL-isoleucine by gamma-irradiation at dry ice temperature. All free radicals induced were decayed concomitant to the successive annealing but the radical species which is believed to be dominant seems to be stable even near the melting point of the ice. These dominant species were found to be identical to those resulted from direct action of radiation in the solid at room temperature. Small but significant changes in the spectra of glycine and DL-${\alpha}$-alanine were observed by varying the microwave power. These results seem to support the view that the spectra obtained were composite consisting of more than two different resonances having different power saturation characteristics. The relative contribution of unidentified resonances to the composite spectra was greater for solutions of low concentration. These resonances are assumed to be induced by indirect effects, mainly hydrogen abstraction by radiation produced hydroxyl radicals and also C-N bond cleavage by hydrated electrons.

An ESR Study of Amino Acid and Protein Free Radicals in Solution Part VI. Enzymatic Inactivation of Lysozyme in Aqueous Solution Resulting from Exposure to $Ti-H_2O_2$ System and Gamma-Irradiation

Hong, Sun-Joo,Piette, L.H. Korean Chemical Society 1972 대한화학회지 Vol.16 No.2

The activity change of lysozyme resulted from its exposure to $Ti-H_2O_2$system in aqueous liquid at room temperature and to ${\gamma}$-irradiation in ice at $195^{\circ}K$ has been measured at room temperature with a Cary-14 spectrophotometer. The enzymatic activity of lysozyme which had been added to a previously flow-mixed solution of $TiCl_3$ and $H_2O_2$ (System I) was compared with the activity of a lysozyme-$H_2O_2$ solution after flow-mixing with $TiCl_3$ (System II), considering the differences between these two activity changes as the extent of the enzymatic inactivation by the involvement of OH radical reaction. The fraction of lysozyme inactivated by OH radical in the system containing 0.0025 M $TiCl_3-0.1M$ $H_2O_2$ (ph 3.5) was 13%, When the $TiCl_3$ concentration is double (pH 3.0), the fraction of enzyme inactivated increases to 36%. The activity of the system containing 0.025 M $TiCl_3-0.1$ M $H_2O_2$ (pH 1.5) was essentially zero. The results seem to support the previos view that the production of OH radical should be proportional to $TiCl_3$ concentration when $H_2O_2$ is present in excess. Increase in the extent of inactivation found in system I with increasing $TiCl_3$ concentration may be due to a pH effect. $H_2O_2$ seems to be less effective than $TiCl_3$ in the inactivation. 1% lysozyme solution, when ${\gamma}$-irradiated with a total dose of 3M rads, loses about 20% of its activity. Lowering of temperature also was found to yield a reduction in enzymatic activity.

AN ESR STUDY OF AMINO ACID AND PROTEIN FREE RADICALS IN SOLUTION PART I. Reaction Mechanism of Free Radical Production in the Ti-$H_2O_2$ Flow System

홍순주,Hong Sun-Joo,L. H. Piette Korean Chemical Society 1971 대한화학회지 Vol.15 No.1

The reaction of amino acids and the reactive hydroxyl radical generated by $Ti^{3+}-H_2O_2$ system was studied using fast flow techniques coupled with ESR. Upon adding methionine to the 0.2M $H_2O_2$ solution (0.05M methionine after addition) and mixing with 0.01M $TiCl_3$, the low field component of the two incompletely resolved peaks, in the spectrum of $Ti^{3+}-H_2O_2$ system alone, vanished completely whereas the high field component remained almost constant and superimposed on the secondary spectrum of the methionine free radical. Similar results were obtained for other amino acids and proteins. The results strongly demonstrate that the $T^{3+}-H_2O_2$ flow system generates two different radical species, only one of which, giving rise to the low field component, is alone responsible for abstracting hydrogen atoms from substrate molecules. The effects of HCl, $H_2SO_4$ and NaOH on the system were also studied with widely varying results.

An ESR Study of Amino Acid and Protein Free Radicals in Solution Part Ⅲ. ESR Study of Lysozyme Free Radical Produced by $Ti-H_2O_2$ Flow System

홍순주,Hong, Sun-Joo,Piette, L.H. Korean Chemical Society 1971 대한화학회지 Vol.15 No.4

Free radicals of lysozyme produced by $Ti-H_2O_2$ system were studied in aqueous solution at room temperature using ESR with a continuous flow-mixing. The spectra, each consisting of a doublet with 5.5 G splitting and a broad resonance covering 80 G splitting are closely similar in shape to that for solid irradiated in vacuum at $77^{\circ}K$ and observed at room temperature immediately on warming. The result is assumed to indicate that the secondary protein radical components formed within 0.01 second, dead time of the mixing chamber, and initiated by hydrogen atom abstraction at ${\alpha}$-carbon atom of peptide chain in liquid solution at room temperature are identical to those resulting from the initial formation of a mixture of positive holes and negative ions by ionization processes as well as radical fragments by the rupture of chemical bonds in the solid during similar time at the same temperature. A broad resonance is observed with considerable amplitude on the high field side of the doublet, which is quite dissimilar to the spectra of irradiated solid lysozyme. This resonance was tentatively attributed to the polypeptide free radical in which unpaired electrons are localized on side chain.