[Serologic investigation of HBV in 302 patients who had a history of smallpox]

This paper provides serologic investigation of HBV in 302 persons who had a history of smallpox in Zhumadian County. The results showed that the HBsAg positivity rate (1.3%) was significantly lower than those of the control group 1 (8.3%) and 2 (8.6%) (P less than 0.001). The HBsAg positivity rate between the two control groups had no significant difference (P greater than 0.05). The HBV infection rate (19.2%) was also lower than those of control group 1 (47.7%) and 2 (51.3%) (P less than 0.001). There was not much difference between the two control groups. The determination of cellular immunity showed that the rosette positivity rate (75.93%) and lymphocyte conversion rate (70.39%) of the patients' group were higher than those of control group 1 (62.3% and 52.9%) and 2 (60.93% and 55.3%). It may suggested that patients having had smallpox might have enhanced cellular immunity which might interfere with HBV infection.

[Toxic principles of Oxytropis glabra DC]

Eight alkaloids were isolated from Oxytropis glabra and identified as anagirine, thermopsine, N-methylcytisine, sparteine, baptifoline, adenine, dictamnine and ethyl allophanate respectively by spectral analysis and physicochemical methods. All these alkaloids were isolated from this genus for the first time and ethyl allophanate was found in nature for the first time.

[Distribution of muscarinic receptors of different affinities in smooth muscle of human stomach]

Muscarinic receptors of high and low affinity were found in the fundus and the body of human stomach through the contraction experiment combined with ligand method in vitro. The 2 types of muscarinic receptors with different affinity regulated respectively the contractions of the longitudinal and the circular muscle of human gastric fundus and gastric body. However, in the antrum exists only one kind of muscarinic receptors of high affinity, which regulated the contractions of the longitudinal and the circular muscles of human stomach. The contractile force of the longitudinal muscle induced by exogenous ACh in the fundus and that in the body of human stomach were found to be similar to each other. The contractile force of the circular muscle in the body was found to be the strongest, and the contractile force of both longitudinal and circular muscles in antrum was weaker.

[Determination of berberine hydrochloride in traditional Chinese medicines containing Coptis chinensis Franch by reversed phase high performance liquid chromatography]

This paper reports a reversed phase high performance liquid chromatography method to determine berberine hydrochloride in Coptis chinensis Franch and in the traditional Chinese medicine containing Coptis chinensis Franch. The result shows that the mobile phase of 0.4mol/L ammonium nitratemethanol (52:48) can give a satisfactory separation. The extraction of sample with 1% H2SO4 solution using the ultrasonic vibration method is simple and easy to operate.

Identification of a peptide inhibitor of the cardiac sarcolemmal Na(+)-Ca2+ exchanger

The deduced amino acid sequence of the cardiac sarcolemmal Na(+)-Ca2+ exchanger has a region which could represent a calmodulin binding site. As calmodulin binding regions of proteins often have an autoinhibitory role, a synthetic peptide with this sequence was tested for functional effects on Na(+)-Ca2+ exchange activity. The peptide inhibits the Na(+)-dependent Ca2+ uptake (KI approximately 1.5 microM) and the Nao(+)-dependent Ca2+ efflux of sarcolemmal vesicles in a noncompetitive manner with respect to both Na+ and Ca2+. The peptide is also a potent inhibitor (KI approximately 0.1 microM) of the Na(+)-Ca2+ exchange current of excised sarcolemmal patches. The binding site for the peptide on the exchanger is on the cytoplasmic surface of the membrane. The exchanger inhibitory peptide binds calmodulin with a moderately high affinity. From the characteristics of the inhibition of the exchange of sarcolemmal vesicles, we deduce that only inside-out sarcolemmal vesicles participate in the usual Na(+)-Ca2+ exchange assay. This contrasts with the common assumption that both inside-out and right-side-out vesicles exhibit exchange activity.

Suppression of splenic macrophage interleukin-1 secretion following intracerebroventricular injection of interleukin-1 beta: evidence for pituitary-adrenal and sympathetic control

Intracerebroventricular (ICV) injections of interleukin-1 beta (IL-1 beta) produced a dose-dependent increase in plasma corticosterone and adrenocorticotropic hormone (ACTH) within 2 hr of injection and then declined over the next 24 hr. Using a potent steroidogenic dose of IL-1 beta (5 ng), ICV injection resulted in suppression of splenic macrophage IL-1 secretion following stimulation by LPS in vitro. Macrophage TGF-beta secretion was not affected, indicating a differential action of ICV IL-1 beta on macrophage cytokine production. Following adrenalectomy (ADX), the suppressive effect of ICV IL-1 beta was reversed and resulted in stimulation of macrophage IL-1 secretion, indicating that the suppression was mediated by adrenocorticol activation. However, surgical interruption of the splenic nerve to eliminate autonomic innervation of the spleen also prevented the macrophage suppressive signal in rats given ICV IL-1 beta. Furthermore, the combination of ADX and splenic nerve section resulted in a potent stimulatory effect of ICV IL-1 beta on splenic macrophage IL-1 secretion which was greater than either ADX or splenic nerve section alone. These results support the concept of a negative feedback on macrophage IL-1 secretion by the central action of IL-1 beta and indicate that both the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system mediate this effect.

Case-control study on pathogenesis of pneumonia in children aged 0-2 years

In order to know the incidence of risk factors predisposing children to pneumonia, case control study was carried out in six MCH Model Counties in 1986. Single factor analysis showed 29 factors were responsible for the increasing incidence of pneumonia. 13 of 29 factors were major pneumonia risk factors by the standard of means greater than 15 and OR greater than 3. They were malnutrition, anemia, riskets, pneumonia history, repeated colds, chronic diarrhoea, congenital malformation, asphyxia neonatorum, amniotic fluid aspiration, artificial feeding, too much clothing, family member with acute respiratory illness (ARI) and contact with ARI patients. Among them 7 factors were related to individual health condition. Therefore, it is important to improve general health of children so as to reduce the incidence of pneumonia.

[Identification of 10 kinds of Zanthoxylum by pyrolysis GC]

In this paper, pyrolysis GC was applied to differentiate and fingerprint 10 kinds of Zanthoxylum on an OV-101 capillary column. Analytical conditions with this column, operating temperature, pyrolysis time and peak identifications are discussed.

[Results of total gastrectomy in the treatment of adenocarcinoma of the cardia in advanced stages]

Over an 8 year period, 66 patients with adenocarcinoma of the cardia in advanced stages underwent total gastrectomy. The operative morbidity rate was 7.5% and the post-operative mortality rate (1 month) was 1.5%. The post-operative 1,3,4, and 5 year survival rates were 69%, 30.7%, 20% and 13.8% respectively. The quality of life after surgery was improved. Pathologic type, lymph node metastasis, incomplete resection and post-operative chemotherapy were the main factors influencing post-operative survival. Indications for total gastrectomy and the advantages of transthoracic total gastrectomy are discussed.

[Changes in induced interleukin-1 and interleukin-2 activity and their interrelationship in patients with schistosomiasis japonica]

Activities of IL-1 produced by peripheral blood monocytes stimulated with lipopolysaccharide and IL-2 released by peripheral blood mononuclear cells induced by PHA, SWAP and SEA in vitro were detected in patients with various stages of schistosomiasis japonica. It was found that the activity of IL-1 was greatly increased and positively related to the body temperature, and high level of IL-2 was induced by SWAP and SEA in the group of acute schistosomiasis. The activity of IL-1 was significantly reduced in the groups of chronic and advanced schistosomiasis, especially in the latter group. The level of IL-2 induced by SWAP and SEA in the groups of chronic and advanced schistosomiasis was significantly lower than that in the group of acute schistosomiasis, but was much higher than that in the group of normal control. The level of IL-2 induced by SWAP and SEA in the cases of acute schistosomiasis was positively related to the activity of IL-1. The results indicate that the specific cellular immunity was increased in acute cases and decreased in chronic cases of schistosomiasis japonica. Both specific and nonspecific cellular immune responses were greatly reduced in cases of advanced schistosomiasis japonica. IL-1 and IL-2 may play an important role in the immunoregulation of schistosomiasis japonica.

Lateral sural cutaneous artery island flap in the treatment of soft tissue defects at the knee

This paper describes a flap for covering defects around the knee. Dissections of 20 legs showed that in the majority the lateral sural cutaneous artery branched from the popliteal artery and descended along the posterolateral aspect of the leg together with two venae comitantes and the lateral sural cutaneous nerve. An island flap was designed, pedicled on these vessels and nerve, and was used in 17 patients with defects around the knee, including acute trauma (three cases), soft tissue tumours (three cases), unstable scar or ulcer (seven cases), and chronic osteomyelitis or infected open fractures with tissue loss (four cases). All the flaps survived entirely and possessed normal sensation. Furthermore, it was not necessary to sacrifice the main vessels of the lower leg.

[Detection of HBAg in the liver in patients with schistosomiasis complicated by liver carcinoma]

HBsAg and HBcAg were detected in the liver biopsies of 21 patients with schistosomiasis japonica complicated by hepatocellular carcinoma (HCC), 69 patients with advanced schistosomiasis japonica and 25 patients with HCC. The positive rate of HBAg in liver of patients with schistosomiasis complicated by HCC (85.7%) was significantly higher than those with advanced schistosomiasis (56.5%), but similar to that in the group of HCC (80.0%). The location of tumor cells in liver was not related with the distribution of schistosomal ova in patients with schistosomiasis complicated by HCC. The results indicate that complicated HBV infection may be one of the major causes of HCC developed in patients with schistosomiasis japonica.

[Chemical evaluation of vinegar-processing method for fresh rhizoma Corydalis]

Qualitative and quantitative analysis were carried out on the samples of Rhizoma Corydalis in both the locally vinegar-processed (fresh) and traditionally vinegar-processed forms. No difference was found in the main chemical constituents. However, both the total alkaloids and the corydalis B content of the former are higher than those of the latter.

[Synthesis of 4-[(4-chlorophenyl) (5-fluoro-2-hydroxyphenyl) methylene amino]butyrates and its anticonvulsant activity]

It is known that gamma-aminobutyric acid (GABA) plays an important role in the pathophysiology of epilepsy. Under physiological conditions it is very difficult for GABA to cross the blood-brain barrier. It is likely that the esters of GABA, Which easily enter the brain, will have useful therapeutic properties. With this in mind, we have designed and synthesized 8 derivatives (IVa to IVh) of gamma-aminobutyric acid with an imine to link a lipophilic carrier in order to facilitate the passage of gamma-aminobutyric acid to cross the blood-brain barrier. All the eight synthesized title compounds were evaluated as anticonvulsants in mice via the Antiepileptic Drug Development Program of NIH. The compounds IVb and IVf showed anticonvulsant activity.

[The phase analyses of radionuclide angiographic images in patients with right bundle branch block, left bundle branch block and Wolff-Parkinson-White syndrome]

The phase analysis of the radionuclide angiographic images in normal subjects, RBBB, LBBB, WPW syndrome of 21, 23, 10, 17 cases respectively was reported. The results of the abnormal conduction groups showed that the parameters of the mean phase angle were delayed as compared with that in the normal group. The mean phase angles were 52.6 +/- 13.4 degrees in the normal group and 85.7 +/- 24.8 degrees, 84.5 +/- 17.4 degrees, 70.0 +/- 40.5 degrees, 78.3 +/- 35.6 degrees in the RBBB, LBBB, WPW-A and WPW-B groups respectively. There was a significant difference between the normal and abnormal conduction groups except for the WPW-A group. Furthermore, the sequential activation of cardiac wall showing the abnormal cardiac conduction could be seen by this method. It seems that phase analysis may be taken as a good noninvasive and adjunctive method for the evaluation of patients with WPW syndrome.

The reverse-flow posterior tibial artery island flap: anatomic study and 72 clinical cases

Based on anatomic, dye injection, and angiography observations since 1984, 72 patients with tissue defects of the foot (due to injury or surgery) have been reconstructed using a reverse-flow posterior tibial artery island flap. In the 72 patients, etiology has included extensive crushing (40 patients), burn scars (10 patients), and tissue loss following tumor or chronic ulcer resection (22 patients). Only two flaps developed necrosis. The survival rate was 97.2 percent, including seven cases of distal marginal necrosis. This procedure, therefore, offers a useful alternative in the repair and reconstruction of extensive tissue defects in the foot, whether caused by accidental injury or surgery.

Efficient plant regeneration from rice protoplasts in general medium

We established an efficient and reproducible procedure for protoplast propagation and fertile plant regeneration of rice (Oryza sativa L.) cultivars Nipponbare and Taipei 309. Selection of scutellum-derived secondary calli, the use of General medium and nurse culture were all found to be critical in the procedure. When 5 basal media (Murashige and Skoog, RY-2, modified R2, Amino Acid and General media) were compared, suspension callus growth rate, protoplast yield and plating efficiency were all about 30% higher in General medium than in the second-best R2 medium. Only one month was required to develop suspension cultures for protoplast isolation using General medium. A plating efficiency as high as 17% and a plant regeneration frequency of 67% were achieved by the improved procedure. Agronomic traits of protoplast- and seed-derived plants were found to be similar.

A polyethylene glycol-mediated protoplast transformation system for production of fertile transgenic rice plants

We have established an efficient procedure for protoplast transformation and regeneration of fertile transgenic plants of rice (Oryza sativa L.) cultivars Nipponbare and Taipei 309. Protoplasts were mixed with a plant-expressible hygromycin resistance gene and treated with 25% (w/v) polyethylene glycol. Stringent selection of transformed colonies was applied to 14-day-old regenerated protoplasts in the presence of 95 micromolar of hygromycin B for 12 days. After selection, 450 and 200 resistant colonies were recovered per million treated Taipei 309 and Nipponbare protoplasts, respectively. Southern hybridization analysis of hygromycin-resistant cell lines and regenerated plants indicated that 1 to 10 copies of transferred DNA were integrated at 1 to 4 loci of the rice genome. Southern DNA analysis suggests that the introduced plasmid DNA may form concatemers by intermolecular recombination prior to integration. Four Taipei 309 and 39 Nipponbare transgenic rice plants were regenerated and grown to maturity in the greenhouse. Two Taipei 309 and 35 Nipponbare plants set viable seeds. Agronomic traits of Taipei 309 transgenic plants and inheritance of the hygromycin resistance trait by progeny of the selfed transgenic plants were analyzed.

Sensory nerve endings in puborectalis and anal region: normal findings in the newborn and changes in anorectal anomalies

This study was carried out in five full-term newborn babies and 11 patients with anorectal anomalies (five of whom had high deformity, five had intermediate, and one had low), using the modified Bielschowsky method. The following four kinds of sensory nerve ending were found: muscle spindle in the puborectalis and the external anal sphincter, Pacinian corpuscle in the plane between the internal anal sphincter and the external anal sphincter and in the presacral space, globular ending in the presacral space, and free nerve ending in the epithelium of the anal canal and in the perianal skin. It was found that there were significantly fewer muscle spindles in the puborectalis and many fewer Pacinian corpuscles and globular endings in the presacral space of high and intermediate deformities than normal. No spindle was found in the external sphincteric muscles of the deformities. On the other hand, the Pacinian corpuscles and the globular endings of high and intermediate deformities lagged behind normal in development. The densities of the nerve bundles in the subepidermis and the nerve fibers in the dermis of perineal region in high and intermediate deformities were much lower than normal, and the decrease in density corresponded to the levels of the rectal pouch. The observation showed that the agenesis of sensory nerve endings in the puborectalis and the anal region was one of the most significant pathological features in high and intermediate types of anorectal anomalies, and might be responsible for the abnormalities of the reflex of the anal sphincter and the anal sensation in such patients.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparative autoradiographic study demonstrating differential intratumor localization of monoclonal antibodies to cell surface (Lym-1) and intracellular (TNT-1) antigens

Autoradiography was utilized to explore the patterns of distribution of two different monoclonal antibodies (Lym-1 and TNT-1) in tumor-bearing nude mice. Lym-1 is an antibody against a cell surface B-cell antigen. In comparison, TNT-1 represents a novel approach and is an antibody against an intracellular (nuclear) antigen that is selectively revealed in degenerating tumor cells. Experimentally iodine-125-(125I) labeled Lym-1 or TNT-1 was injected intravenously into nude mice bearing either the Raji lymphoma or the ME-180 human cervical carcinoma. Qualitative autoradiographic analyses performed after injection revealed that Lym-1 accumulated at the periphery of the target tumor where vascular permeability is marked and where Lym-1 positive cells are first encountered. By contrast, TNT-1 lost its initial peripheral distribution and demonstrated progressive concentration in the center of the tumor where binding to its nuclear antigen is facilitated by the presence of cell degeneration and necrosis. These studies confirm the ability of TNT-1 to bind areas deep within tumor that traditionally are considered inaccessible to antibodies administered for imaging and therapy.

[Comparison of birth defects prevalence rates between hospital and community based surveillance data]

Birth defects surveillance (BDS) data of Cangzhou area, Hebei province in 1986 was studied to compare the prevalence rate from hospital based data (HBD) with that from community based data (CBD). Of 7,742 total births, 4,245 (55%) were born in the county hospitals and above, and 3,497 (45%) in the township hospitals and homes. The birth defects prevalence rate (BDPR) from HBD was 30.9 per 1,000 total births, while that from CBD was 10.5 per 1,000 total births. The difference was statistically significant (P less than 0.05). It was found that the higher BDPR from HBD was associated with the greater percentage of high risk pregnancies who delivered at the hospitals and who had higher risk of birth defects. The relationship of BDPRs between HBD and CBD, and others potential related factors need to be further studied.

Function and localization of high and low affinity binding sites to muscarinic receptors in longitudinal and circular smooth muscles of human stomach

The contractile response to acetylcholine (ACh) and the binding of [3H]-quinuclidinyl benzilate [( 3H]QNB) to muscarinic receptors in both longitudinal and circular muscles were examined in fundus, body and antrum of human stomach which was obtained by surgical operation for gastric cancer or ulcer. The values of pD2 and pA2 for ACh and atropine, respectively, on longitudinal muscle of fundus were similar to those of body but were larger than those of antrum. On the other hand, the values of pD2 and pA2 on circular muscles were not different among fundus, body, and antrum and were similar to those on longitudinal muscle of antrum. By Scatchard analysis of receptor binding of [3H]QNB in homogenate, at least two subclasses of binding sites, i.e. high and low affinity sites, were observed in fundus and body, while only high affinity binding site was found in antrum. Thus, we conclude that there are at least two subclasses of muscarinic receptors which regulate the contraction of smooth muscle in different regions of human stomach.

Regulatory elements of the human vimentin gene: activation during proliferation

We investigated the constitution of the vimentin regulatory region through the use of cloned deletion mutants and the nucleotide sequence analysis in order to determine the elements which are implicated in the various physiological stimulations. We report that the vimentin promoter is constituted of a juxtaposition of at least 20 different putative regulatory elements illustrating the molecular tinkering theory. Fifty-eight motifs were found, representing 20 different sequences. Each of these mini-elements displays a consensus sequence homologous to or closely related to that found in regulatory regions of different genes correlated with processes of cell activation and proliferation.

Angled side wall microarteriotomy scissors: a new end-to-side microvascular anastomosis instrument

Creation of a smooth side wall arteriotomy for an end-to-side microsurgical anastomosis can at times be difficult and time consuming. To facilitate this maneuver, a new end-to-side microarteriotomy scissor was designed for creation of recipient vessel openings from 0.5-2 mm in size. These new scissors and their recommended use are described.

[Comparative study on the reflex responses of carotid and aortic baroreceptors in the rabbit]

In 81 anesthetized rabbits, the baroreflex control of heart rate (HR), hind-limb vascular resistance (HVR) and renal sympathetic nerve activity (RSNA) was observed during arterial baroreceptor loading and unloading by intravenously injecting phenylephrine (PE) and nitroprusside (NP). The results were as follows: (1) An increase of arterial pressure with PE caused reduction in HR, HVR and RSNA, while a decrease of arterial pressure with NP evoked opposite responses. These reflex responses were reproducible. (2) By either carotid baroreceptor denervation (CBRX) or aortic baroreceptor denervation (ABRX), the reflex changes of HR induced by injecting PE and NP were impaired (P less than 0.01), while the reflex responses in HVP remained unchanged. Despite of the enhanced basal RSNA following ABRX or CBRX, the magnitude of reflex inhibition in RSNA during injecting NP was similar to that before denervation, whereas that of the reflex excitation in RSNA during injecting NP was reduced (P less than 0.05). (3) After complete sino-aortic denervation (SAD), the change of arterial pressure following PE or NP injection was enhanced, but the reflex changes in HR, HVR and RSNA were significantly diminished (P less than 0.001). (4) Vagotomy abolished the residual reflex changes observed after SAD. The results indicate that the aortic and carotid baroreceptors may regulate HR in a simple additive manner, while the aortic baroreceptor seems to be more important. Furthermore, both the aortic and carotid baroreceptors may play important roles for the reflex control of HVR and RSNA, and operate mutually by the way of inhibitory summation.

[Arterial baroreflex in the renal hypertensive rabbits]

In 14 anesthetized male rabbits subjected bilateral renal wrapping 12 weeks before, the baroreflex control of heart rate (HR), hindlimb vascular resistance (HVR) and renal sympathetic nerve activity (RSNA) was examined during arterial baroreceptor loading and unloading by injecting phenylephrine (PE) and nitroprusside (NP). The results were as follows: (1) The mean arterial pressure (131 +/- 9 mmHg) of the kidney-wrapped rabbits was significantly higher than that (95 +/- 10 mmHg) of the control rabbits (P less than 0.001). (2) With the buffer nerves intact, the baroreflex control of HR was obviously impaired in the hypertensive rabbits (P less than 0.01), whereas the reflex control of HVR and RSNA remained unchanged as compared with the normotensive rabbits (P greater than 0.05), indicating a dissociation of baroreflex control of HR from that of peripheral circulation. However, in response to local intraarterial injection of PE and NP, the changes in HVR showed no difference between the hypertensive and normotensive rabbits. (3) After aortic or carotid baroreceptor denervation, the reflex control of HR was further reduced in the hypertensive rabbits, and the reflex control of HVR and RSNA was also significantly reduced (P less than 0.01), suggesting an impairment of potential baroreflex regulation of the circulation. It is likely that the changes of baroreflex in hypertensive rabbits may be attributed to the abnormalities in both baroreceptor and central integrating mechanism.

Evidence for ligand-induced conformational changes in proteins from phosphorescence spectroscopy

Phosphorescence spectroscopy on mouse myeloma IgA J539 in rigid solution at 77K revealed the type of anomalous short-lived component in the tryptophan decay originally observed with lysozyme (Churchich, J.E., 1966. Biochim. Biophys. Acta. 120:406-412) and seen in a large number of Bence Jones proteins (Longworth, J.W., C.L. McLaughlin, and A. Solomon. 1976. Biochemistry. 15:2953-2958). The decay time of the anomalous component that results from the interaction between tryptophan side chains and disulfide linkages in proteins was observed to significantly lengthen in J539 in response to binding of a galactan antigen. With hen egg-white lysozyme in which the type of fluorescence enhancement on ligand binding seen with J539 has also been observed, phosphorescence measurements revealed a similar lengthening of the decay time of the disulfide-induced anomalous component in the tryptophan decay. These perturbations are interpreted as ligand-induced changes to the tryptophan-disulfide proximities that have been shown to exist in these structures. Given the short-range nature of the disulfide perturbation (see following article) the observations suggest, in particular when combined with x-ray crystallographic data, that phosphorescence decay-time measurements of disulfide perturbations can serve as a sensitive spectroscopic indicator of subtle conformational changes in immunoglobulins and other tryptophan-disulfide containing proteins.

Distance dependence of the tryptophan-disulfide interaction at the triplet level from pulsed phosphorescence studies on a model system

In the present study the distance dependence of tryptophan-disulfide interaction is examined with a view to both utilizing the interaction as a more quantitative indicator of subtle conformational changes in proteins as well as elucidating the interaction mechanism. To examine perturbations specifically at the indole triplet level 2-(3-indolyl)-ethyl phenyl ketone (IEPK) in which excitation is transferred with high efficiency to the triplet state of the indole moiety was employed. Phosphorescence decays of IEPK excited by a laser pulse in 70/30 (vol/vol) ethanolether at 77 K were measured in the presence of various concentrations of simple disulfides. The nonexponential phosphorescence decays arising from a distribution of fixed chromophoreperturber separations and the steady-state quenching of IEPK were accounted for with an exponential dependence of the quenching rate constant with distance. The small effective Bohr radius (0.8 A) that appears in the exponent emphasizes the localized nature of the interaction. Comparison of the triplet quenching rate constant obtained at quencher contact with IEPK to that estimated in proteins suggests a dependence on the triplet energy of the indole moiety and an endothermic nature for the quenching process. The study predicts that in proteins tryptophan-disulfide interactions are very localized in nature and should give rise to detectable anomalous decays only out to 2 A beyond van der Waals contact between the interacting partners.