Table 1.

In silico study of putative molecular residual interactions between recombinant Fel d 1 (rFel d 1) and the compounds and assessment of their capabilities to displace N-phenyl-1-naphthylamine (1-NPN).

n°	Compound Names	Estimated Free Energy of Binding (kcal/mol)	Total Intermolecular Energy (kcal/mol)	Frequency	H-Bond Residue	Hydrophobic Residue (Alkyl/Pi-Alkyl/Pi-Sigma)	In Silico Screening a	1-NPN Displacement Screening
Fatty Acids and Other Derivatives
1	Isobutyric acid	−2.96	−3.26	27%		A88, Y119, L129	No	ND
2	Capric Acid	−5.16	−7.4	23%		L61, F80, V83, F84	No	No
3	Lauric Acid	−5.84	−8.58	60%	Y119	L61, F80, V83, F84	Yes	Yes
4	Myristic Acid	−3.35	−7.02	36%	F84	F13, V133, M134, I137	Yes	Yes
5	Palmitic Acid	−2.33	−5.88	16%	F84	V133, M134	Yes	Yes
6	Oleic Acid	−2.82	−7.05	50%	M134	I64, F80, V83	Yes	Yes
7	Linoleic Acid	−2.95	−6.88	40%	P78	A88, Y119, L129	Yes	Yes
8	Dodecanal	−4.88	−7.42	2%		F84, M134	No	No
9	Dodecanol	−3.93	−7.02	2%		F84, V133, M134	No	No
10	Tetradecanol	−3.97	−7.89	6%		P78, Y81	No	No
11	Ethyl Laurate	−4.7	−8.02	12%	F84	L61, I64, F80, V83, V133, M134, I137	Yes	No
12	Methyl Palmitate	−2.53	−6.67	20%	T76		Yes	No
13	Nonanamide	−4.53	−6.51	4%		L61, I64, V83, F80	No	ND
14	Hexadecanamide	−2.84	−6.3	18%	T135	Y81	Yes	ND
15	Octadecanamide	−2.81	−6.96	6%	G131	Y81, F85	Yes	ND
Steroids
1	Androstenone	−5.84	−5.84	65%	S138	P78, Y81, F85	Yes	Yes
2	Androstenedione	−5.83	−5.83	44%		Y81, F85	Yes	Yes
3	Androstenol	−5.06	−5.36	22%		Y81, F85	No	No
4	Progesterone	−5.74	−6.04	62%	T76	Y81, F85	Yes	Yes
5	Hydroxyprogesterone	−5.14	−5.54	39%	Y81	F85	Yes	Yes
6	Pregnenolone	−5.59	−6.17	58%	T76	Y81, F85	Yes	Yes
7	Estradiol	−4.94	−5.54	26%	T76	Y81, F85	Yes	Yes
8	Testosterone	−5.6	−5.9	35%	T76	Y81, F85	Yes	Yes
9	Dihydrotestosterone	−5.06	−5.35	12%		Y81, F85	No	No
10	Estrone	−3.56	−3.86	10%	D82, G131	F85	Yes	Yes
11	Dehydroepiandrosterone (DHEA)	−4.64	−4.94	30%		Y81, F85	Yes	Yes
12	Corticosterone	−5.35	−6.38	30%	T76, N89	Y81, F85	Yes	No
13	Deoxycorticosterone	−4.99	−5.29	12%		Y81, F85	No	No
Fluorescent Probe
1	1-NPN (Central)	−6.7	−7.41	50%	Y119	L14, L61, M112	Yes	/
2	1-NPN (Surface)	−4.74	−5.45	30%		Y81, F85	Yes	/

ND: Not determined because of the fluorescence increase, probably due to non-specific hydrophobic interactions [42]. ^a The in silico screenings were considered to result in positive outcomes (“yes”) if the following were predicted: (1) minimum one H-bond interaction irrespective of the binding frequency or (2) ≥30% of binding frequency without H-bond. This threshold value of binding frequency (≥30%) was selected from the minimum binding frequency of the fluorescent probe (1-NPN) with rFel d 1.