Biochemistry

Biochemistry

REVIEW O F 1955 DEN TAL RESEA RCH . . . V O LU M E 52, A PR IL 1956 • 419 treatment are discussed by Korkhaus.12 Although his paper cannot be conside...

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REVIEW O F 1955 DEN TAL RESEA RCH . . . V O LU M E 52, A PR IL 1956 • 419

treatment are discussed by Korkhaus.12 Although his paper cannot be considered a research report in a strict sense, Kork­ haus applies his own and the research ob­ servations of others to clinical problems. He points out the importance played by the changes in the incisor and buccal arch segments in the transition through the mixed to the permanent dentition. He also points out that natural forces can be used by the orthodontist in a planned and methodical way. Three contributions of Bjork deserve mention: the description of a method for studying jaw growth which uses metallic implants and cephalometry;13 a study of the various factors concerned with over­ jet, their quantitative effect and inter­ action ;14 and the relation of bite develop­ ment and body build.15

2. P h illip s , J. R. A p i c a l r o o t r e s o r p t io n u n d e r o r t h o ­ d o n t ic t h e r a p y . A n g l e O r t h o d o n t . 25:1 J a n . 1955. 3. R ick etts, R. M . F a c ia l a n d d e n t u r e c h a n g e s d u r i n g o r t h o d o n t ic t r e a t m e n t a s a n a ly s e d fr o m the t e m p o r o ­ m a n d ib u la r jo in t. A m . J. O r t h o d o n t . 41:163 M a r c h 1955. 4. K o s k i, K. N o r m c o n c e p t in d e n t a l A n g l e O r t h o d o n t . 25:113 A p r i l 1955.

o r t h o p e d ic s .

5. P en ce , W . C l i n i c a l a n d h is t o lo g i c s t u d y o f th e p a t h o l o g y o f th e g i n g i v a e d u r i n g o r t h o d o n t ic t h e r a p y . N orth w e st. U n iv . D. School B ull. (R e se a rch and G r a d u a t e S t u d ie s ) 55:12 F e b . 21, 1953. 6. G o r e lic k , L. O n th e use o f p a c if ie r s in p r e v e n t in g m a lo c c lu s io n . N e w Y o r k D .J . 21:3 J a n . 1955. 7. B jo rk, A . C r a n ia l b a s e d e v e lo p m e n t . A m . J . O r t h o ­ d o n t . 41:198 M a r c h 1955. 8. P e rk in s, A p r i l 1955.

G.

C r a n io p h o r o m e t e r .

J .A .O .A .

50:441

9. P o p o v ic h , F. C e p h a l o m e t r i c e v a lu a t io n o f v e r t ic a l o v e r b it e in y o u n g a d u lt s . J . C a n a d . D . A . 21:209 A p r i l 1955. 10. K o s k i, K., a n d V tr o la in e n , K a ija . R e la t io n o f h ts1lin e to th e n a s a l f lo o r . A r o e n t g e n o l o g ic c e p h a lo m e t r ic s t u d y . D . R e c o r d 75:45 F e b . - M a r c h 1955. 11. L u n d s t r o m , A . In t e r m a x illa r y t o o t h w id th r a t io and tooth a li g n m e n t and o c c lu s io n . A cta o d o n t. S c a n d i n a v . 12:266 F e b . 1955. 12. K o rk h a u s , _ G . F o r c e s in v o lv e d in s e lf- c o r r e c t in g o c c lu s a l a n o m a lie s a n d t h e ir a p p li c a t io n to th e e a r ly o r t h o d o n t ic t r e a tm e n t . In t e rn a t. D .J . 5:3 M a r c h 1955. 13. B jork, A . F a c ia l g r o w t h in m a n , st u d ie d w ith th e a id o f m e t a llic im p la n t s . A c t a o d o n t . S c a n d in a v . 13:9 J u n e 1955. 14. Bjork, A ., a n d P a llin g , M o g e n s . A d o l e s c e n t a g e c h a n g e s in s a g it t a l ¡a w r e la t io n , a lv e o l a r p r o g n a t h y , a n d in c is a l in c lin a t io n : A c t a o d o n t . S c a n d in a v . 12:201 F e b . 1955.

I. H u e tt n e r , R., a n d Y o u n g , R. M o v a b i l i t y o f v it a l 15. Bjork, A . B ite d e v e lo p m e n t a n d d e v it a liz e d te e th in th e M a c a c u s rh e s u s m o n k e y . R e c o r d 75:8 J a n . 1955. O r a l S u r g ., O r a l M e d . , & O r a l P ath . 8:189 F e b . 1955.

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BIOCHEMISTRY Harold C. H odge, Ph.D., Rochester, N. Y.

Summarizing the interesting and impor­ tant papers published in biochemistry during the past year would be a lengthy and highly technical job of doubtful in­ terest in many aspects to most dental readers. An attempt has been made, therefore, to select high lights of extra­ ordinary accomplishments. NATURE OF THE VIRUS The tobacco mosaic virus has been torn into inactive fragments; that is, two prin­ cipal constituents, nucleic acid and pro­

tein. These were recombined into the active, infective virus by H. L. Fraenkel Conrat and Robley Williams1 of the Virus Laboratory of the University of California. Two processes were employed to obtain the fragments; (1) the virus was treated with sodium lauryl sulfate which tore the protein off of the thin thread of nucleic acid that constitutes the central fiber of the virus rod, and (2) from other samples the protein was U n iv e r s it y o f R o c h e ste r, S c h o o l o f M e d i c i n e a n d tistry.

Den­

420 • T H E JO U R N A L O F TH E A M ER IC A N DENTAL A S SO C IA TIO N

obtained free from nucleic acid by treat­ ment with sodium carbonate. Treatment of the protein alone with acid caused lit­ tle doughnut-shaped objects to be formed as seen in an electron micrograph; these were inactive. Treatment of the protein with acid in the presence of the nucleic acid formed a virus rod; this was active (infective). The protein apparently wrapped itself around a nucleic acid thread like the lead in a lead pencil to make the virus rod. This rod had the properties of living tobacco mosaic virus. The first crystallization of a virus that is infective for man or animals was also achieved in the Virus Laboratory of the University of California by C. E. Schwerdt and F. L. Schaffer.2 The polio virus was obtained from a monkey kid­ ney (specifically the MEF—I, Type II polio). The kidney protein contained about 1 part in 10,000 of active virus by weight. By suitable solution and digestive procedures, the contaminating proteins were reduced to such an extent that on storage in the cold some of the polio virus crystallized. It was found that the crystalline virus was fully infective for monkeys. STRUCTURE OF VITAMIN Bi 2 The structure of the vitamin B12 mole­ cule, the cobalt-containing vitamin, was announced by Sir Alexander Todd and his colleagues of the Cambridge Labora­ tory (England). Chemical work in the past few years had led to the identifica­ tion of many of the important parts of the structure. The roentgen ray crystallographic findings of Dorothy Hodgkin3 and her group at Oxford were sent to the University of California at Los An­ geles where Kenneth N. Trueblood and colleagues using the UNIVAC computer developed a three dimensional electron density projection “which revealed almost every structural feature of the molecule and provided the key to the B12 iden­ tification.” The B12 vitamin is the “heav­

iest and most complicated non-protein material in nature.” The proof of the exact structure of this extremely com­ plicated vitamin is a milestone. SYNTHESIS OF ALDOSTERONE The principal life-maintaining hormone of the adrenal cortex, aldosterone, was synthesized in a brilliant chemical at­ tack announced by Alfred Wettstein,4 from the laboratories of Ciba, University of Basle, Swiss Federal Institute of Tech­ nology, and N. V. Organon (Nether­ lands). Starting with a relatively simple tricyclic compound, the one used by Sarett and co-workers in synthesizing the natural isomer of cortisone, Wettstein and colleagues carried through 30 syn­ thetic steps to the final crystalline aldo­ sterone. The crystalline material had in microgram quantities the biological prop­ erties of sodium retention and potassium excretion exhibited by the natural aldo­ sterone. In the past, huge amounts of beef and pig adrenals have been worked up to obtain the hormone; about 100 mg. per ton of adrenal is the usual yield. Clinical evaluation of the synthetic ma­ terial will be made to decide whether commercial production will be under­ taken. STRUCTURE OF PROTEIN Several years ago Li and his colleagues at the University of California obtained protein from the anterior lobe of a pitui­ tary gland that had all of the properties of adrenal cortex stimulation associated with ACTH. In the meantime, it was found by the same workers that purifica­ tion of the protein by ion exchange meth­ ods led to the isolation of a polypeptide having a molecular weight of about 6,500, known as corticotropin A. During the past year, Li and colleagues5 have announced the amino acid sequence of corticotropin A. By pepsin or trypsin hy­ drolysis, mixtures of short chained poly­

REVIEW O F 1955 DENTAL RESEA RCH .

peptides were obtained. These polypep­ tides were separated by chromatography, each spot was eluted and further hy­ drolysed. Each hydrolysis mixture was then separated by chromatography and the final individual amino acids or, in some cases, the dipeptides, were identi­ fied by chromatographic procedures. Chymotrypsin and acid hydrolysis were also used. By analyzing fractions that must have been adjacent, Li and col­ leagues were able to line up 19 polypep­ tides and show that the amino acid se­ quence could be resolved into a list of 39 amino acid residues in the order in which they occur along the chain of alpha corticotropin. Another major step in the identifica­ tion of the precise chemical nature of insulin was made by Sanger and col­ leagues6 using somewhat similar tech­ nics. Insulin fractions A and B were sub­ jected to hydrolysis by a protease from mold (also by a papain) ; the fragments were separated by iontophoresis and iden­ tified by suitable chromatographic analy­ ses. The fractions bearing amide groups differed in their mobilities under ionto­ phoresis. Each fraction was analyzed for the amide content. Fraction A with four amide groups has been shown to be made up of 21 amino acids in sequence. Fraction B with two amide groups has 30 amino acids in sequence.

• V O L U M E 52, A P R IL I95& • 421

SYNTHESIS OF A RIBOSE NUCLEIC ACID Grunberg-Manago, Ortiz, and Ochoa7 reported the enzymatic synthesis of a material apparently identical with the biologically occurring ribonucleic acid. The key to this synthesis came earlier when an enzyme, polynucleotide phosphorylase, was obtained from a micro­ organism, Azotobacter vinelandii. This enzyme catalyzes the synthesis of poly­ nucleotides from nucleotide diphosphates releasing orthophosphate. The mixture of adenine diphosphate, guanine diphos­ phate, uridine diphosphate and cytidine diphosphate was subjected to the action of the polynucleotide phosphorylase, and a polymer of high molecular weight was obtained which “appears to be indistin­ guishable from native RNA.” 1. F r a e n k e l- C o n r a t , a c t iv a t io n o f t o b a c c o 33:4794 N o v . 7, 1955.

H . L., a n d W i ll ia m s , R. { R e ­ m o s a ic v ir u s ) . C h e m . E n g . N e w s

2. S c h w e r d t, C . E., a n d Sc h a ffe r, F. L. ( C r y s t a l l i z a ­ t io n o f p o l io v ir u s ) . C h e m . E n g . N e w s 33:4795 N o v . 7, 1955. 3. H o d g k i n , D . C ., a n d o th e rs . S t r u c tu r e o f v it a m in Bi2 N a t u r e 176:325, 1955; se e a ls o p . 328. S e e a ls o C h e m . E n g . N e w s 33:3487, 1955 " q u o t e d . "

.

4. W e tt s te in , A . ( S y n th e sis E n g . N e w s 33:3486, 1955.

of

a ld o s t e r o n e ) .

5. Li, C . H ., a n d o th e rs . A m i n o a c id a lp h a c o r t ic o t r o p i n . N a t u r e 176:687, 1955.

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6. S a n g e r , F.; T h o m p s o n , E. O . P., a n d K ita i, R. T h e a m id e g r o u p s o f In su lin . B io c h e m . J . 59:509, 1955. 7. G r u n b e r g - M a n a g o , M . ; O r t iz , P. J., a n d O c h o a , S. E n z y m a t ic sy n t h e s is o f n u c le ic a c id - lik e p o l y n u c le o ­ t id e s . S c ie n c e 122:907, 1955.

Scientific Progress * In science, no advance is final. Every problem solved produces new ques­ tions to answer, since evefry higher step gives us a w ider outlook, and the pow er o f seeing problems w hich from a lower level were not apparent. Ernest Starling.