1. Introduction
Emesis, commonly referred to as vomiting, is a well-recognized physiological reflex that can be triggered by various peripheral and central stimuli [
1]. These stimuli encompass gastrointestinal irritation or inflammation, the presence of cancer chemotherapy, circulating toxins and other pharmacological agents, pain, anxiety, and motion that provokes a response [
2]. The defensive reflex is a commonly observed phenomenon in both animals and humans. In contrast, nausea is a subjective experience characterized by a disagreeable sensation closely linked to the act of vomiting [
3].
The pathophysiology of vomiting is characterized by a significant degree of complexity. The reticular formation encompasses a vomiting center (VC) which can be stimulated by afferent stimuli originating from the gastrointestinal tract or by the chemoreceptor trigger zone (CTZ) [
4,
5]. The latter is commonly regarded as the primary site for the induction of emesis resulting from the administration of various cancer chemotherapeutic agents and toxic compounds [
6,
7]. Some pharmaceutical agents that are incapable of traversing the blood-brain barrier can be employed to specifically target it [
8]. Besides the CTZ, various anatomical sites such as the gastrointestinal tract (GIT), higher cortical centers, the vestibular system, and the thalamus have been recognized as consistent stimuli for the initiation of emesis [
9]. The ventral VC located in the reticular formation can be stimulated through the convergence of afferent stimuli originating from the GIT or by the CTZ [
10,
11]. Moreover, the VC assumes a crucial function in orchestrating the contractions of smooth muscles and skeletal activities linked to the emetic process [
12,
13]. The close proximity between the nucleus tractus solitaries (NTS) and the CTZ may elicit a reaction at the CTZ in the presence of emetogenic chemicals in the bloodstream or cerebrospinal fluid (CSF) [
14,
15]. Furthermore, the CTZ plays a regulatory role in various physiological processes, including the control of food intake, conditioned taste aversion, and GIT motility [
16,
17]. The initiation of emesis occurs when the CTZ detects emetogenic toxins in the bloodstream and CSF [
18]. This detection is facilitated by various receptors within the CTZ, such as, serotonin receptor (5HT3), muscarinic acetylcholine receptors (M1-M4), dopamine receptors (D2, D3), histamine (H1), neurokinin 1 receptor (NK1) for substance P and opioid receptors [
19,
20,
21]. Once these receptors detect the emetogenic toxins, they transmit a signal to the nearby NTS [
22,
23]. The NTS functions as the principal mechanism by which all emetic stimuli elicit the physiological response of vomiting, providing a comprehensive final pathway. During the act of emesis, the abdominal muscles undergo a retrograde contraction while the lower esophageal sphincter relaxes, facilitating the expulsion of stomach contents through the oral cavity and inducing retching [
24,
25].
Dopamine receptors are vital to the performance of several critical processes in everyday life. There are five distinct subtypes of dopamine receptors [
26]. The D2 receptor has a role in several cognitive and behavioral processes, including movement, attention, sleep, memory, and learning [
27]. The D2 receptor plays a vital role in the physiology of eliciting emesis [
28]. The precise signaling processes behind the induction of vomiting by the D2 receptor have yet to be elucidated. The research evidence suggests that the activation of extracellular signal-regulated kinase (ERK), phosphatidylinositol-3 kinases (PI3K), and protein kinase C (PKC)-related signaling cascades via the D2 receptor might possibly lead to the occurrence of emesis [
29,
30].
At present, a diverse range of antiemetic medications that are approved for clinical use are utilized in the treatment and control of symptoms associated with nausea and vomiting. The medications can be classified into various categories, such as anti-dopaminergic drugs, serotonin antagonists, antihistamines, NK1-receptor inhibitors, anticholinergic drugs, and receptor agonists for corticosteroids, GABA
B, and cannabinoid receptor type 1 (CB1) [
31,
32]. The extended utilization of synthetic antiemetic medications is also associated with various adverse effects, such as muscle weakness, spasms, or convulsions [
33,
34]. Hence, natural products have become a crucial requirement in contemporary society owing to their minimal adverse effects and economic advantages [
10,
35]. Current efforts in the exploration of new antiemetic drugs derived from natural sources are primarily centered around mechanism-based strategies that target specific cellular and molecular mechanisms. Polysaccharides, flavonoids, alkaloids, diterpenes, glucosides, cannabinoids, diarylheptanoids, chalcones, saponins, hydroxycinnamic acids, phenylpropanoids, terpenes, and lignans encompass a wide range of bioactive compounds that are of interest in the exploration of potential candidates for the development of antiemetic drugs [
10,
17].
The compound known as Quercetin (QUA), with its IUPAC name being 2-(3, 4-dihydroxy phenyl)-3,5,7-trihydroxychromen-4-one, is a polyphenolic flavonoid that exhibits a broad distribution. A diverse array of fruits, vegetables, grains, and leaves, such as grapes, green tea, apples, citrus fruits, berries, cherries, capers, leafy greens, kale, and red onions, are known to contain compounds that exhibit a broad spectrum of health-promoting effects in relation to various diseases [
36,
37,
38]. QUA possess a wide range of applications in the production of nutritional supplements, beverages, and food products [
39]. According to numerous studies, QUA has been found to possess various pharmacological activities, including but not limited to anticancer [
40], antioxidant [
41], anti-obesity [
42], anti-aging [
43], anti-inflammatory [
44], antidiabetic [
45], antiallergic [
46], cardioprotective [
47], immune modulatory [
48], neuroprotective [
49], antiviral, and antimicrobial effects [
50]. In a study conducted by Lee et al. (2005), the researchers examined the impact of QUA on the activity of the mouse 5HT3 channel, a receptor known to be involved in the physiological process of vomiting [
51].
On the other hand, the utilization of computational methodologies in the field of drug discovery and development facilitates the efficient examination of a large collection of compounds and the anticipation of potential binding agents through the application of modeling, simulation, and visualization techniques. Furthermore, this approach aids in the anticipation of pharmacokinetics, toxicity, and binding sites, all of which play a pivotal role in elucidating mechanistic processes and identifying and cultivating promising drug candidates [
52,
53]. The primary objective of this study is to evaluate the potential antiemetic effect of QUA in chick (
in vivo). Additionally, we also carried out an
in silico study to identify potential molecular interactions with the emesis inducing receptors underlying the observed effect.
4. Discussion
Inadequate management of chemotherapy-induced nausea and vomiting (CINV) can significantly impact functional capabilities and may compromise treatment compliance [
65]. The oral ingestion of toxic CuSO
4.5H
2O can lead to a distinct vagal emetic response due to its properties as an oxidizing agent and its corrosive effects on the gastrointestinal mucous membranes [
66,
67,
68]. The induction of emesis occurs as a result of peripheral mechanisms, which involve the stimulation of visceral afferent nerve fibers in the gastrointestinal tract [
69]. These stimuli are then transmitted to the vomiting center [
70,
71]. Recent findings demonstrated that 5HT3, D2, D3, H1, and M1-M5 receptors are present at the stimulation site and contribute to the induction of emesis. Antagonists of the 5HT3, D2, D3, H1, and M1-M5 receptors have the ability to prevent or significantly decrease emesis induced by chemotherapeutic agents [
72,
73].
The chosen standard drug, DOM, exhibited peripheral selectivity as an antagonist for D2 and D3 receptors [
74]. Its mechanism of action involves the inhibition or antagonism of these receptors at the CTZ in the brain, thereby facilitating the desired therapeutic effects [
75]. During our investigation, the group DOM ingestion displayed a mean value of 11.80 ± 2.09 retches in chicks, while the mean value of retches in the NC group was 64.25 ± 3.69. The administration of OND and HYS decreased the frequency of retching episodes in the chick group compared to the control group receiving the vehicle. Based on empirical findings, it is possible to postulate that QUA demonstrated a safeguarding influence against toxicity by mitigating or preventing neural signals responsible for eliciting emetic responses. The significant reduction in the frequency of retches observed in both QUA groups compared to the NC group supports this notion, with the obtained mean values being 16.50 ± 4.65 and 10.00 ± 4.19 for the QUA-25 and QUA-50 groups, respectively. These values are close to or better than the standard groups. On the contrary, the different PC groups (DOM, OND, and HYS) administered to the animals demonstrated longer latency periods compared to the NC group. Specifically, the latency periods were 61.00 ± 3.34, 16.17 ± 3.64, and 11.50 ± 2.38 seconds for DOM, OND, and HYS, respectively. Interestingly, the treatment group (QUA-50) exhibited the highest latency period among all PC the groups. The result shows that QUA-50 is more effective in reducing retches and prolonging latency periods compared to the standard DOM, OND, and HYS groups in CuSO
4.5H
2O-mediated emesis.
In the field of pharmacology, the phenomenon where the combined impact of multiple medications surpasses the individual effects observed when each drug is administered in isolation is referred to as a synergistic effect or synergism [
76]. Our experimental study demonstrated that using a combined drug therapy resulted in a reduction in the occurrence of retches and an increase in the duration of the latency period in chicks, indicating the presence of a synergistic effect. Previous research has shown that administering antiemetic drugs effectively delays the occurrence of nausea or vomiting in response to emetic stimuli induced by cancer chemotherapy or acute toxicity [
77]. Our study observed that the test combined group (DOM + QUA 50) displayed a significantly prolonged latency period of (156.67 ± 2.40) seconds compared to the NC group.
In a study conducted by Wang and Borison (1951) and Niijima et al. (1987), it was observed that CuSO
4.5H
2O does not exhibit the expected response to vagal nerve stimulation. Specifically, the researchers observed that vagotomy could not prevent emesis, a procedure that involves severing the distal portion of the vagus nerve in the gastrointestinal tract [
78,
79]. This suggests that the emetic response to CuSO
4.5H
2O may involve chemoreceptor signaling.
Figure 7 illustrates a possible antiemetic mechanism of QUA and standard drugs.
Molecular docking is a computational methodology employed to investigate the compatibility of a ligand with a receptor binding site, taking into consideration both geometric and energetic factors [
80,
81,
82]. The estimation of the interaction level between a ligand and a receptor is accomplished by assessing their binding affinity [
83]. The binding interactions between QUA and the D2 receptor were higher compared to other receptors involved in the induction of emesis. The binding energy of QUA with D2 was -9.7 kcal/mol, whereas the binding energy of standard DOM was -9.8 kcal/mol. The drug-receptor interaction visualization indicates that the binding sites for QUA and DOM were SER193, TYR416, THR119, CYS118, ASP114, TRP386, and PHE390 for QUA, and SER409, ASP114, PHE389, VAL91, LEU94, TYR408, and TRP413 for DOM. Multiple studies have consistently provided evidence indicating that the activation of D2 receptors triggers the vomiting center located in the CTZ [
84,
85,
86]. QUA effectively inhibits the response of the D2 receptor, thereby impeding dopamine activity. Therefore, it can be confidently concluded that QUA exhibits strong inhibitory potency for the D2 receptor compared to other receptors responsible for emesis. This conclusion is supported by the higher docking scores of QUA with D2 receptors compared to other receptors. Additionally,
in vivo, combined therapy with DOM+QUA-50 had shown higher efficacy than other combinations.
Drug discovery and development is a protracted, financially burdensome, and precarious undertaking, spanning 10 to 15 years on average [
87]. The approval of a novel pharmaceutical for clinical application entails an average expenditure exceeding
$1 to
$2 billion [
88]. The drug candidate undergoes rigorous optimization during the preclinical stage before progressing to the phase I clinical trial [
89]. Approximately 90% of drug candidates fail during the progression of clinical studies, specifically during phase I, II, and III clinical trials, primarily due to issues related to toxicity and a lack of clinical efficacy [
90,
91,
92].
In silico toxicological investigations play a crucial and significant role in safe and cost-effective drug development [
93]. In our present study, QUA demonstrated no toxic effects on hepatotoxicity, immunotoxicity, and cytotoxicity. However, it did exhibit toxicity effects in terms of carcinogenicity and mutagenicity.
The study indicates that QUA exhibits significant antiemetic effects in response to CuSO4.5H2O-induced emesis, potentially attributed to its ability to antagonize D2 receptors. The in vivo findings also suggest that the antiemetic efficacy of QUA remains consistent and dependable when administered at a reduced dosage.
Studies using certain laboratory animals provide necessary and important data regarding the beneficial and harmful effects of new drug candidates and their possible biopharmaceutical considerations [
94]. Thus, each pre-clinical study helps medicinal scientists evaluate biologically active molecules potential for clinical studies. These studies allow for the determination of test dose and dosage frequency, the right administration routes, the drug metabolism profile, and the development of error correction machines during clinical trials. In this study, we have seen that all standard anti-emetic drugs clearly inhibit the emesis tendency in animals. The test sample's QUA also exerted dose-dependent anti-emetic effects in animals. In comparison to the control and standard groups, QUA exerted strong anti-emetic effects in animals. Although this well known drug candidate is yet to undergo extensive toxicological studies in animal models, in this study QUA treatment did not show any toxicological phenomena, nor did it cause the death of any chicks, which demonstrates its safety in this animal model. Moreover, our
in-vivo findings also corroborate the outcomes of
in-silico studies, demonstrating the possibility of considering this bioactive in the emesis of laboratory animals.
The major limitation of this study is that the findings may be influenced by various factors, such as the differences in physiology and geometry of the animal’s stomach and the digestive capability of foods taken before the test started, which also impact emesis induction. Another possible limitation is the placement of the gavage tube at the time of inducer (copper sulfate) delivery in the gastric compartment; therefore, it is difficult to determine the specific chemical placement and timing of movement of the emetic agent along the GI tract. In addition, this is a physiologic behavioral experiment; in this case, all animals would not respond similarly due to the variance of the environment, such as laboratory light, noise during the experiment, and test time differences, though we followed the optimum laboratory protocols mentioned in the study design section.
Author Contributions
Conceptualization, R.C., M.S.B., and M.T.I.; data curation, M.S.B. and R.H; Methodology A.I.R, R.H., H.D.M.C.; formal analysis; M.S.B., A.I.R., H.D.M.C. and I.M.A.; investigation, M.S.B., R.H., and R.C., resources, A.I.R. and MT.I., software, H.D.M.C. and I.R.A.d.M; validation, I.M.A. and I.R.A.M.; visualization, A.I.R., M.S.B., H.D.M.C., and R.C., writing-original draft, R.C., and M.S.B., writing review & editing, R.C., H.D.M.C., I.R.A.d.M., A.I.M. and M.T.I., supervision, M.T.I., project administration, I.R.A.d.M. and M.T.I.
Figure 1.
Structures of quercetin and selected reference drugs screened against the emesis inducing receptor.
Figure 1.
Structures of quercetin and selected reference drugs screened against the emesis inducing receptor.
Figure 2.
Latency (sec) of retches observed in test sample, controls and combinations. [Values are mean ± S.E.M. (n = 5). acompared to the NC (vehicle), bcompared to the DOM (PC); ccompared to the OND; dcompared to the HYS; ecompared to the QUA-25; fcompared to the QUA-50; gcompared to the DOM+QUA-50; hcompared to the OND+QUA-50; p<0.05 (OND+QUA-50 vs HYS+QUA-50); p<0.0001(NC vs DOM, NC vs QUA-25, NC vs QUA-50, NC vs DOM+QUA-50, NC vs OND+QUA-50, NC vs HYS+QUA-50, DOM vs OND, DOM vs HYS, DOM vs QUA-50, DOM vs DOM+QUA-50, DOM vs OND+QUA-50, DOM vs HYS+QUA-50, OND vs QUA-25, OND vs QUA-50, OND vs DOM+QUA-50, OND vs OND+QUA-50, OND vs HYS+QUA-50, HYS vs QUA-25, HYS vs QUA-50, HYS vs DOM+QUA-50, HYS vs OND+QUA-50, HYS vs HYS+QUA-50, QUA-25 vs QUA-50, QUA-25 vs DOM+QUA-50, QUA-25 vs OND+QUA-50, QUA-25 vs HYS+QUA-50, QUA-50 vs DOM+QUA-50, QUA-50 vs OND+QUA-50, QUA-50 vs HYS+QUA-50, DOM+QUA-50 vs HYS+QUA-50).
Figure 2.
Latency (sec) of retches observed in test sample, controls and combinations. [Values are mean ± S.E.M. (n = 5). acompared to the NC (vehicle), bcompared to the DOM (PC); ccompared to the OND; dcompared to the HYS; ecompared to the QUA-25; fcompared to the QUA-50; gcompared to the DOM+QUA-50; hcompared to the OND+QUA-50; p<0.05 (OND+QUA-50 vs HYS+QUA-50); p<0.0001(NC vs DOM, NC vs QUA-25, NC vs QUA-50, NC vs DOM+QUA-50, NC vs OND+QUA-50, NC vs HYS+QUA-50, DOM vs OND, DOM vs HYS, DOM vs QUA-50, DOM vs DOM+QUA-50, DOM vs OND+QUA-50, DOM vs HYS+QUA-50, OND vs QUA-25, OND vs QUA-50, OND vs DOM+QUA-50, OND vs OND+QUA-50, OND vs HYS+QUA-50, HYS vs QUA-25, HYS vs QUA-50, HYS vs DOM+QUA-50, HYS vs OND+QUA-50, HYS vs HYS+QUA-50, QUA-25 vs QUA-50, QUA-25 vs DOM+QUA-50, QUA-25 vs OND+QUA-50, QUA-25 vs HYS+QUA-50, QUA-50 vs DOM+QUA-50, QUA-50 vs OND+QUA-50, QUA-50 vs HYS+QUA-50, DOM+QUA-50 vs HYS+QUA-50).
Figure 3.
Number of retches observed in test sample, controls and combinations. [Values are mean ± S.E.M. (n = 5). acompared to the NC (vehicle), bcompared to the DOM (positive control); ccompared to the OND; dcompared to the HYS; p<0.05 (NC vs HYS, OND vs QUA-25); p<0.01 (DOM vs OND, OND vs HYS, OND vs HYS+QUA-50); p<0.001 (OND vs QUA-50, OND vs OND+QUA-50); p<0.0001 (NC vs DOM, NC vs OND, NC vs QUA-25, NC vs QUA-50, NC vs DOM+QUA-50, NC vs OND+QUA-50, NC vs HYS+QUA-50, DOM vs HYS, OND vs DOM+QUA-50, HYS vs QUA-25, HYS vs QUA-50, HYS vs DOM+QUA-50, HYS vs OND+QUA-50, HYS vs HYS+QUA-50).
Figure 3.
Number of retches observed in test sample, controls and combinations. [Values are mean ± S.E.M. (n = 5). acompared to the NC (vehicle), bcompared to the DOM (positive control); ccompared to the OND; dcompared to the HYS; p<0.05 (NC vs HYS, OND vs QUA-25); p<0.01 (DOM vs OND, OND vs HYS, OND vs HYS+QUA-50); p<0.001 (OND vs QUA-50, OND vs OND+QUA-50); p<0.0001 (NC vs DOM, NC vs OND, NC vs QUA-25, NC vs QUA-50, NC vs DOM+QUA-50, NC vs OND+QUA-50, NC vs HYS+QUA-50, DOM vs HYS, OND vs DOM+QUA-50, HYS vs QUA-25, HYS vs QUA-50, HYS vs DOM+QUA-50, HYS vs OND+QUA-50, HYS vs HYS+QUA-50).
Figure 4.
The best Molecular docking interaction of the D2 receptor with (A) QUA or (B) DOM compound.
Figure 4.
The best Molecular docking interaction of the D2 receptor with (A) QUA or (B) DOM compound.
Figure 5.
The best Molecular docking interaction of the 5HT3 receptor with (A) QUA or (B) OND compound.
Figure 5.
The best Molecular docking interaction of the 5HT3 receptor with (A) QUA or (B) OND compound.
Figure 6.
The best molecular docking interaction of the M4 receptor with (A) QUA or (B) HYS compound.
Figure 6.
The best molecular docking interaction of the M4 receptor with (A) QUA or (B) HYS compound.
Figure 7.
The proposed mechanism of action for the antiemetic effects of QUA, OND, DOM, and HYS is based on their binding affinity with the D2, 5HT3, and M4 receptors [Briefly, QUA is evident to bind with 5HT3 (Lee et al., 2005). Our in silico studies suggest that it can also bind with D2 and M4 receptors. Upon going through the literature report and our present study, we suppose QUA may inhibit these three receptors. On the other hand, both DOM and OND display inhibitory effects on D2 and 5HT3 receptors, respectively, while HYS specifically blocks M4 receptor. By antagonizing these stomach receptors, these drugs prevent the stimulation of the vomiting center located in the medulla oblongata in animals. As a result, there is a lack of gastrointestinal tract contraction, muscle contraction, and initiation of efferent signals to organs, ultimately, inhibiting emesis].
Figure 7.
The proposed mechanism of action for the antiemetic effects of QUA, OND, DOM, and HYS is based on their binding affinity with the D2, 5HT3, and M4 receptors [Briefly, QUA is evident to bind with 5HT3 (Lee et al., 2005). Our in silico studies suggest that it can also bind with D2 and M4 receptors. Upon going through the literature report and our present study, we suppose QUA may inhibit these three receptors. On the other hand, both DOM and OND display inhibitory effects on D2 and 5HT3 receptors, respectively, while HYS specifically blocks M4 receptor. By antagonizing these stomach receptors, these drugs prevent the stimulation of the vomiting center located in the medulla oblongata in animals. As a result, there is a lack of gastrointestinal tract contraction, muscle contraction, and initiation of efferent signals to organs, ultimately, inhibiting emesis].
Table 1.
Percentage increase in latency and decrease in retches in treatment groups retches observed in test and referral groups.
Table 1.
Percentage increase in latency and decrease in retches in treatment groups retches observed in test and referral groups.
Name of group |
%Increase in latency |
%Decrease in retches |
NC (vehicle) |
- |
- |
DOM |
86.48 |
81.63 |
OND |
48.98 |
52.06 |
HYS |
28.26 |
24.00 |
QUA-50 |
91.25 |
84.43 |
QUA-25 |
86.08 |
74.32 |
DOM+QUA-50 |
94.73 |
90.66 |
OND+QUA-50 |
94.36 |
87.04 |
HYS+QUA-50 |
93.56 |
81.01 |
Table 2.
The best results of a molecular docking study of QUA and DOM with two (D2 and D3) receptors.
Table 2.
The best results of a molecular docking study of QUA and DOM with two (D2 and D3) receptors.
Receptors |
Binding Affinity |
No. of HB |
HB residues |
HB length (Å) |
Other bond residues |
D2-QUA |
-9.7 |
4 |
SER193 TYR416 THR119 CYS118 |
1.85 2.20 2.14 2.18 |
ASP114 TRP386 PHE390 |
D3-QUA |
-8.5 |
3 |
VAL189 TYR365 VAL111 |
2.36 2.09 3.56
|
ASP110 ILE183 PHE345 HIS349 VAL107 ILE183 |
D2-DOM |
-9.8 |
1 |
SER409 |
1.89
|
ASP114 PHE389 VAL91 LEU94 TYR408 TRP413 |
D3-DOM |
-9.4 |
3 |
GLY1107 VAL1103 PHE1104 |
2.83 1.77 3.53
|
GLU1011 ASP1020 LEU1032 ALA1074 |
Table 3.
The best results of a molecular docking study of QUA and OND with 5HT3 receptors.
Table 3.
The best results of a molecular docking study of QUA and OND with 5HT3 receptors.
Receptors |
Binding Affinity |
No. of HB |
HB residues |
HB length (Å) |
Other bond residues |
5HT3-QUA |
-7.9 |
2 |
ILE267 ASP271 |
2.51 2.95
|
ILE268 LEU266 ILE267 LEU234 PRO230 |
5HT3-OND |
-8.1
|
- |
- |
- |
LEU234 VAL264 |
Table 4.
The best results of a molecular docking study of QUA and HYS with five (M1, M2, M3, M4, and M5) receptors.
Table 4.
The best results of a molecular docking study of QUA and HYS with five (M1, M2, M3, M4, and M5) receptors.
Receptors |
Binding Affinity |
No. of HB |
HB residues |
HB length (Å) |
Other bond residues |
M1-QUA |
-7.8
|
2 |
TYR106 ILE180 |
2.03 2.77 |
TYR404 |
M2-QUA |
-8.2
|
2 |
PHE181 TYR104 |
2.43 1.96 |
TRP422 |
M3-QUA |
-9
|
2 |
TRP206 ARG183 |
2.08 3.22
|
ARG171 MET187 VAL210 TYR175 |
M4-QUA |
-9.2
|
2 |
TYR416 SER436 |
2.54 2.06 |
PHE186 TRP435 |
M5-QUA |
-8
|
2 |
ILE185 HIS478 |
2.76 2.19 |
TYR481 TRP477 |
M1-HYS |
-7.1 |
4 |
THR189 CYS178 TYR404 LEU183 |
2.01 2.33 3.62 3.41 |
TYR179 |
M2-HYS |
-7.5 |
- |
- |
- |
TYR426 |
M3-HYS |
-8.6
|
2 |
ASN507 TYR529 |
2.26 3.47
|
CYS532 TYR148 TRP503 TYR506 ALA235 |
M4-HYS |
-8.9
|
3 |
TYR92 ASP432 ASN423 |
2.81 2.71 3.70 |
TYR439 PHE186 TRP435 |
M5-HYS |
-7.7
|
|
ILE185 HIS478 SER189 |
1.93 2.62 2.95 |
TRP477 TYR481 |