Search for chemical structures by a sketch :C8H10ClNO3

Computed Properties of C8H10ClNO3. About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Pishchugin, FV; Tuleberdiev, IT or concate me.

Computed Properties of C8H10ClNO3. Authors Pishchugin, FV; Tuleberdiev, IT in MAIK NAUKA/INTERPERIODICA/SPRINGER published article about in [Pishchugin, F. V.; Tuleberdiev, I. T.] Kyrgyz Natl Acad Sci, Inst Chem & Phytotechnol, Bishkek 720071, Kyrgyzstan in 2021.0, Cited 13.0. The Name is 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. Through research, I have a further understanding and discovery of 65-22-5

The kinetics and mechanism of condensation of pyridoxal hydrochloride with L-alpha-asparagine, L-alpha- and D-alpha-aspartic acids are analyzed via UV spectroscopy and polarimetry. It is found that L-alpha-asparagine containing alpha-NH2 and gamma-NH2 groups interacts with pyridoxal via the gamma-NH2 group, forming Schiff bases that are resistant to chemical transformations. Rearrangement produces Schiff bases that form the cyclic structure from the amino acid moiety. L-alpha- and D-alpha-aspartic acids interacting with pyridoxal via alpha-NH2 groups create Schiff bases that form quinoid structures after elimination of alpha-hydrogen or CO2. Their subsequent hydrolysis results in pyridoxamine, alpha-ketoacids, and aldehyde acids, respectively. Schemes of the condensation mechanisms of L-alpha-asparagine, L-alpha-, D-alpha-aspartic acids with pyridoxal hydrochloride are proposed.

Computed Properties of C8H10ClNO3. About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Pishchugin, FV; Tuleberdiev, IT or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

The important role of Phenyl(pyridin-2-yl)methanone

About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Cinarli, M; Cinarli, E; Ataol, CY; Idil, O; Kariptas, E or concate me.. Quality Control of Phenyl(pyridin-2-yl)methanone

Quality Control of Phenyl(pyridin-2-yl)methanone. In 2019.0 J MOL STRUCT published article about CRYSTAL-STRUCTURE; SPECTROSCOPIC CHARACTERIZATION; INTERMOLECULAR INTERACTIONS; ANTIBACTERIAL ACTIVITY; COORDINATION BEHAVIOR; BIOLOGICAL-ACTIVITY; CHEMICAL ACTIVITY; DIAZO-COMPOUNDS; SCHIFF-BASES; X-RAY in [Cinarli, Murat] Ahi Evran Univ, Cent Res & Applicat Lab, TR-40100 Kirsehir, Turkey; [Cinarli, Esra] Ahi Evran Univ, Fac Sci, Dept Biol, TR-40100 Kirsehir, Turkey; [Ataol, Cigdem Yuksektepe] Cankiri Karatekin Univ, Fac Sci, Dept Phys, TR-18100 Cankiri, Turkey; [Idil, Onder] Amasya Univ, Fac Educ, Dept Basic Educ, TR-05000 Amasya, Turkey; [Kariptas, Ergin] Ahi Evran Univ, Fac Med, Dept Microbiol, TR-40100 Kirsehir, Turkey in 2019.0, Cited 65.0. The Name is Phenyl(pyridin-2-yl)methanone. Through research, I have a further understanding and discovery of 91-02-1.

The NNO tridentate Schiff base ligand of 2-benzoyl pyridine sulfonyl hydrazone (HL) and its transition metal complexes [CoL2] (1), [NiL2] (2) and [ZnL2] (3) have been synthesized and characterized by analytical and spectroscopic studies. The molecular structures of HL and [NiL2] (2) have been investigated by X-ray diffraction and DET/B3LYP methods. Based on the optimized structures, a single point energy calculation was made for HL and (2) in the different solvent media. The stability of the molecular structures was investigated in different solvent environments by calculating the molecular orbital energies and total energies of the molecular structures. The global reactivity parameters were obtained and the interactions between the molecules with DNA bases such as adenine, cytosine, guanine, and thymine were investigated by using the ECT (electrophilicity-based charge transfer) method and Delta N (charge transfer). Hirshfeld surfaces of HL and (2) complex were investigated and the interaction energies between the molecules participating in C-H center dot center dot center dot O/pi interactions in the molecular structures were calculated by using the CE-HF energy model. From elemental analysis data, the metal-ligand ratio of the complexes was found to be 1:2. All compounds were examined for their antimicrobial activity against pathogenic microorganisms by the well-diffusion method. DNA cleavage studies of compounds were screened by the agarose gel electrophoresis method. The results showed that complex (3) showed highly nicking activity, while HL, (1) and (2) complexes didn’t show any nicking activity. (C) 2019 Elsevier B.V. All rights reserved.

About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Cinarli, M; Cinarli, E; Ataol, CY; Idil, O; Kariptas, E or concate me.. Quality Control of Phenyl(pyridin-2-yl)methanone

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

Chemical Properties and Facts of 65-22-5

Category: pyridine-derivatives. About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Oguro, Y; Nakamura, A; Kurahashi, A or concate me.

Category: pyridine-derivatives. In 2019.0 J BIOSCI BIOENG published article about THERMAL-STABILITY; ACID; PH in [Oguro, Yoshifumi; Nakamura, Ayana; Kurahashi, Atsushi] Hakkaisan Brewery Co Ltd, 1051 Nagamori, Minamiuonuma, Niigata 9497112, Japan in 2019.0, Cited 22.0. The Name is 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. Through research, I have a further understanding and discovery of 65-22-5.

Koji amazake, prepared from rice koji, is a traditional Japanese sweet beverage. The main source of sweetness is glucose derived from rice starch following digestion by enzymes of Aspergillus oryzae during saccharification. The temperature of this process was empirically determined as 45 degrees C-60 degrees C, but no studies have systematically investigated the effect of temperature on saccharification efficiency. We addressed this in the present study by evaluating saccharification efficiency at various temperatures. We found that glucose content was the highest at 50 degrees C (100%) and was reduced at temperatures of 40 degrees C (66.4%), 60 degrees C (91.9%), and 70 degrees C (76.6%). We previously reported that 12 types of oligosaccharides are present in koji amazake; the levels of eight of these, namely nigerose, kojibiose, trehalose, isomaltose, gentiobiose, raffinose, panose, and isomaltotriose, were the highest at 50 degrees C-60 degrees C, whereas sophorose production was maximal at 70 degrees C. Based on these findings, we initially performed saccharification at 50 degrees C and then switched the temperature to 70 degrees C. The maximum amount of each saccharide including sophorose that was produced was close to the values obtained at these two temperatures. Thus, oligosaccharide composition of koji amazake is dependent on saccharification temperature. These findings provide useful information for improving the consumer appeal of koji amazake by enhancing oligosaccharide content. (C) 2018, The Society for Biotechnology, Japan. All rights reserved.

Category: pyridine-derivatives. About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Oguro, Y; Nakamura, A; Kurahashi, A or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

Awesome and Easy Science Experiments about Ethyl nicotinate

COA of Formula: C8H9NO2. About Ethyl nicotinate, If you have any questions, you can contact Dhotre, BK; Raut, SV; Khandebharad, AU; Pathan, A or concate me.

Recently I am researching about ONE-POT SYNTHESIS; 2,5-DISUBSTITUTED-1,3,4-OXADIAZOLES; 1,3,4-OXADIAZOLES; DESIGN; ACIDS, Saw an article supported by the . COA of Formula: C8H9NO2. Published in MAIK NAUKA/INTERPERIODICA/SPRINGER in NEW YORK ,Authors: Dhotre, BK; Raut, SV; Khandebharad, AU; Pathan, A. The CAS is 614-18-6. Through research, I have a further understanding and discovery of Ethyl nicotinate

An efficient acid-catalyzed condensation between substituted benzohydrazides and 2,3,5,6-tetrafluoroterephthalic acid to form 1,4-bis(5-aryl-1,3,4-oxadiazol-2-yl)-2,3,5,6-tetrafluorobenzenes is reported. The products were isolated in 74-87% yield and were characterized by(1)H NMR, IR, and mass spectra.

COA of Formula: C8H9NO2. About Ethyl nicotinate, If you have any questions, you can contact Dhotre, BK; Raut, SV; Khandebharad, AU; Pathan, A or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

Brief introduction of Phenyl(pyridin-2-yl)methanone

Computed Properties of C12H9NO. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Palav, A; Misal, B; Ganwir, P; Badani, P; Chaturbhuj, G or concate me.

Computed Properties of C12H9NO. In 2021 TETRAHEDRON LETT published article about SELECTIVE OXIDATION; N-BROMOSUCCINIMIDE; SULFATED POLYBORATE; BENZYLIC ALCOHOLS; EFFICIENT; CATALYST; ALDEHYDES; COMPLEX; DERIVATIVES; WATER in [Palav, Amey; Misal, Balu; Ganwir, Prerna; Chaturbhuj, Ganesh] Inst Chem Technol, Mumbai 400019, Maharashtra, India; [Palav, Amey; Misal, Balu] Loba Chem Pvt Ltd, Res & Dev Ctr, Tarapur 401506, Thane, India; [Badani, Purav] Univ Mumbai, Dept Chem, Mumbai 400098, Maharashtra, India in 2021, Cited 42. The Name is Phenyl(pyridin-2-yl)methanone. Through research, I have a further understanding and discovery of 91-02-1.

Chlorine is the 20th most abundant element on the earth compared to bromine, iodine, and fluorine, a sulfonimide reagent, N-chloro-N-(phenylsulfonyl)benzenesulfonamide (NCBSI) was identified as a mild and selective oxidant. Without activation, the reagent was proved to oxidize primary and secondary alcohols as well as their symmetrical and mixed ethers to corresponding aldehydes and ketones. With recoverable PS-TEMPO catalyst, selective oxidation over chlorination of primary and secondary alcohols and their ethers with electron-donating substituents was achieved. The reagent precursor of NCBSI was recovered quantitatively and can be reused for synthesizing NCBSI. (C) 2021 Elsevier Ltd. All rights reserved.

Computed Properties of C12H9NO. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Palav, A; Misal, B; Ganwir, P; Badani, P; Chaturbhuj, G or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

Can You Really Do Chemisty Experiments About Phenyl(pyridin-2-yl)methanone

HPLC of Formula: C12H9NO. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Hou, P; Sun, JW; Wang, HJ; Liu, L; Zou, LW; Chen, S or concate me.

Recently I am researching about LARGE STOKES SHIFT; TURN-ON PROBE; CELLULAR THIOLS; LIVING CELLS; REDOX; HOMOCYSTEINE; CONJUGATE; HYDRAZINE; APOPTOSIS; ROLES, Saw an article supported by the Natural Science Foundation of Heilongjiang Province of ChinaNatural Science Foundation of Heilongjiang Province [LH2019B033]. Published in ELSEVIER SCIENCE SA in LAUSANNE ,Authors: Hou, P; Sun, JW; Wang, HJ; Liu, L; Zou, LW; Chen, S. The CAS is 91-02-1. Through research, I have a further understanding and discovery of Phenyl(pyridin-2-yl)methanone. HPLC of Formula: C12H9NO

A novel fluorescent probe, TCF-IPY, has been designed and developed for highly selective and ratiometric detection of GSH based on the extend of the pi-conjugation system of imidazo[1,5-alpha]pyridine IPY-CHO. Upon addition of GSH, TCF-IPY displayed remarkable fluorescence variations (approximate 949-fold ratio changes) from 603 nm to 475 nm, thereby enabling GSH detection in a fine ratiometric manner. Moreover, TCF-IPY exhibited excellent selectivity toward GSH over other biologically related species including Cys and Hcy. The huge blue shifts both in absorption (259 nm) and emission spectra (128 nm), low cytotoxicity, high sensitivity (97 nM) and rapid response (240 s) of TCF-IPY make it a robust molecular tool for endogenous GSH investigation. Furthermore, TCF-IPY was also successfully used for ratiometric imaging of endogenous GSH in living MCF-7 cells and zebrafish.

HPLC of Formula: C12H9NO. About Phenyl(pyridin-2-yl)methanone, If you have any questions, you can contact Hou, P; Sun, JW; Wang, HJ; Liu, L; Zou, LW; Chen, S or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

Discovery of 3-Pyridinecarboxaldehyde

Formula: C6H5NO. About 3-Pyridinecarboxaldehyde, If you have any questions, you can contact Zha, GF; Fang, WY; Leng, J; Qin, HL or concate me.

Formula: C6H5NO. Zha, GF; Fang, WY; Leng, J; Qin, HL in [Zha, Gao-Feng; Fang, Wan-Yin; Leng, Jing; Qin, Hua-Li] Wuhan Univ Technol, Sch Chem Chem Engn & Life Sci, 205 Luoshi Rd, Wuhan 430070, Hubei, Peoples R China published A Simple, Mild and General Oxidation of Alcohols to Aldehydes or Ketones by SO2F2/K2CO3 Using DMSO as Solvent and Oxidant in 2019.0, Cited 67.0. The Name is 3-Pyridinecarboxaldehyde. Through research, I have a further understanding and discovery of 500-22-1.

A practical, general and mild oxidation of primary and secondary alcohols to carbonyl compounds proceeds in yields of up to 99% using SO2F2 as electrophile in DMSO as both the oxidant and the solvent at ambient temperature. No moisture- and oxygen-free conditions are required. Stoichiometric amount of inexpensive K2CO3, which generates easy to separate by-products, is used as the base. Thus, 5-gram scale runs proceeded in nearly quantitative yields by a simple filtration as the work-up. The use of a polar solvent such as DMSO, which usually promotes competing Pummerer rearrangement, is also noteworthy. This protocol is compatible with a variety of common N-, O-, and S-functional groups on (hetero)arene, alkene and alkyne substrates (68 examples). The protocol was applied (99% yield) to a formal synthesis of the important cholesterol-lowering drug Rosuvastatin.

Formula: C6H5NO. About 3-Pyridinecarboxaldehyde, If you have any questions, you can contact Zha, GF; Fang, WY; Leng, J; Qin, HL or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

What advice would you give a new faculty member or graduate student interested in a career 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride

Name: 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Hwang, S; Ryu, JY; Jung, SH; Park, HR; Lee, J or concate me.

An article Cobalt complexes containing salen-type pyridoxal ligand and DMSO for cycloaddition of carbon dioxide to propylene oxide WOS:000523754500006 published article about CYCLOHEXENE OXIDE; HIGHLY EFFICIENT; METAL-CATALYSTS; COPOLYMERIZATION; CO2; EPOXIDES in [Hwang, Saem; Ryu, Ji Yeon; Jung, Sung Hoo; Park, Hyoung-Ryun; Lee, Junseong] Chonnam Natl Univ, Dept Chem, 300 Yongbong Dong, Gwangju 500757, South Korea in 2020.0, Cited 33.0. Name: 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. The Name is 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. Through research, I have a further understanding and discovery of 65-22-5

Cobalt complexes containing a salen-type pyridoxal ligand with pyridine were synthesized as a new Co (III) catalytic system for the cycloaddition of carbon dioxide. Two cobalt(III) complexes possessing a salen-type pyridoxyl ligand were synthesized by the reaction of pyridoxal ligands (pyr(2)en = (N,N’-bis (pyridoxylideneiminato)ethylene) and pyr(2)cy = (N,N’-bis(pyridoxylideneiminato)cyclohexane)) and Co (OAc)(2) and characterized by various analytical methods, including infrared spectroscopy and high-resolution mass analysis. Single-crystal X-ray crystallography analysis confirmed that the cobalt pyr(2)en complex had a distorted octahedral structure: the tetradentate Schiff base ligand binds the cobalt metal in one plane, and the metal center adopts an octahedral geometry by the additional coordination of acetate and dimethyl sulfoxide. The synthesized complexes were used as catalysts in the cycloaddition of carbon dioxide (CO2) to propylene oxide. The catalysts showed high activity for cycloaddition between CO2 and epoxides, even at a low loading (0.5 mol%), in the presence of various cocatalysts. (C) 2020 Elsevier Ltd. All rights reserved.

Name: 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride. About 3-Hydroxy-5-(hydroxymethyl)-2-methylisonicotinaldehyde hydrochloride, If you have any questions, you can contact Hwang, S; Ryu, JY; Jung, SH; Park, HR; Lee, J or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

The Absolute Best Science Experiment for Ethyl nicotinate

Name: Ethyl nicotinate. About Ethyl nicotinate, If you have any questions, you can contact Kreutzer, D; Ritter, CA; Hilgeroth, A or concate me.

In 2020 PHARMACEUTICALS-BASE published article about P-GLYCOPROTEIN; RESIDUES in [Kreutzer, David; Hilgeroth, Andreas] Martin Luther Univ Halle Wittenberg, Inst Pharm, Res Grp Drug Dev, D-06108 Halle, saale, Germany; [Ritter, Christoph A.] Ernst Moritz Arndt Univ Greifswald, Inst Pharm, Dept Clin Pharm, D-17489 Greifswald, Germany in 2020, Cited 27. The Name is Ethyl nicotinate. Through research, I have a further understanding and discovery of 614-18-6. Name: Ethyl nicotinate

Cancer is a strong global burden with increasing numbers of diseases and ongoing anticancer drug resistance. The number of structurally novel anticancer drugs is strongly limited. They cause high costs for the social health systems. Most critical so-called multidrug resistances (MDR) are caused by transmembrane efflux pumps that transport drugs with various structures out of the cancer cells. Multidrug resistance proteins (MRPs) type 1 and 2 are found overexpressed in various kinds of cancer. There is a strong need for inhibitors of those efflux pumps. We developed novel nonsymmetrical 1,4-dihydropyridines as novel inhibitors of cancer relevant MRP types 1 and 2. The structure-dependent activities of the differently substituted derivatives were evaluated in cellular assays of respective cancer cells and are discussed. Promising candidates were identified. One candidate was demonstrated to resensitize a cisplatin resistant cancer cell line and thus to overcome the anticancer drug resistance.

Name: Ethyl nicotinate. About Ethyl nicotinate, If you have any questions, you can contact Kreutzer, D; Ritter, CA; Hilgeroth, A or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem

Some scientific research about 500-22-1

Formula: C6H5NO. About 3-Pyridinecarboxaldehyde, If you have any questions, you can contact Manetti, D; Garifulina, A; Bartolucci, G; Bazzicalupi, C; Bellucci, C; Chiaramonte, N; Dei, S; Mannelli, LD; Ghelardini, C; Gratteri, P; Spirova, E; Shelukhina, I; Teodori, E; Varani, K; Tsetlin, V; Romanelli, MN or concate me.

In 2019.0 J MED CHEM published article about ACETYLCHOLINE-RECEPTORS; IN-VITRO; QUINOLINE DERIVATIVES; THERAPEUTIC TARGETS; LIGAND EFFICIENCY; FULL AGONIST; ALPHA-4-BETA-2; VARENICLINE; EPIBATIDINE; SUBTYPES in [Manetti, Dina; Bartolucci, Gianluca; Bellucci, Cristina; Chiaramonte, Niccolo; Dei, Silvia; Teodori, Elisabetta; Romanelli, Maria Novella] Univ Florence, Sect Pharmaceut & Nutraceut Sci, Dept Neurosci Psychol Drug Res & Childs Hlth NEUR, Via Ugo Schiff 6, I-50019 Sesto Fiorentino, Italy; [Garifulina, Alexandra; Spirova, Ekaterina; Shelukhina, Irina; Tsetlin, Victor] Russian Acad Sci, Shemyakin Ovchinnikov Inst Bioorgan Chem, Dept Mol Basis Neurosignaling, Miklukho Maklaya St 16-10, Moscow 117997, Russia; [Bazzicalupi, Carla] Univ Florence, Dept Chem Ugo Schiff, Via Lastruccia 3, I-50019 Sesto Fiorentino, Italy; [Mannelli, Lorenzo Di Cesare; Ghelardini, Carla] Univ Florence, Sect Pharmacol & Toxicol, Dept NEUROFARBA, Viale G Pieraccini 6, I-50139 Florence, Italy; [Gratteri, Paola] Univ Firenze, Lab Mol Modeling Cheminformat, Dept NEUROFARBA, Via Ugo Schiff 6, I-50019 Sesto Fiorentino, Italy; [Gratteri, Paola] Univ Firenze, QSAR, Via Ugo Schiff 6, I-50019 Sesto Fiorentino, Italy; [Varani, Katia] Univ Ferrara, Inst Pharmacol, Via Fossato di Mortara 17-19, I-44100 Ferrara, Italy in 2019.0, Cited 64.0. The Name is 3-Pyridinecarboxaldehyde. Through research, I have a further understanding and discovery of 500-22-1. Formula: C6H5NO

A three-dimensional database search has been applied to design a series of endo- and exo-3-(pyridin-3-yl)bicyclo[2.2.1]heptan-2-amines as nicotinic receptor ligands. The synthesized compounds were tested in radioligand binding assay on rat cortex against [H-3]-cytisine and [3H]-methyllycaconitine to measure their affinity for alpha 4 beta 2* and alpha 7* nicotinic receptors. The new derivatives showed some preference for the alpha 4 beta 2* over the alpha 7* subtype, with their affinity being dependent on the endo/exo isomerism and on the methylation degree of the basic nitrogen. The endo primary amines displayed the lowest K-i values on both receptor subtypes. Selected compounds (1a, 2a, 3a, and 6a) were tested on heterologously expressed alpha 4 beta 2, alpha 7, and alpha 3 beta 2 receptors and on SHSY-5Y cells. Compounds 1a and 2a showed alpha 4 beta 2 antagonistic properties while behaved as full agonists on recombinant alpha 7 and on SHSYSY cells. On the alpha 3 beta 2 subtype, only the chloro derivative 2a showed full agonist activity and submicromolar potency (EC50 = 0.43 mu M). The primary amines described here represent new chemotypes for the alpha 7 and alpha 3* receptor subtypes.

Formula: C6H5NO. About 3-Pyridinecarboxaldehyde, If you have any questions, you can contact Manetti, D; Garifulina, A; Bartolucci, G; Bazzicalupi, C; Bellucci, C; Chiaramonte, N; Dei, S; Mannelli, LD; Ghelardini, C; Gratteri, P; Spirova, E; Shelukhina, I; Teodori, E; Varani, K; Tsetlin, V; Romanelli, MN or concate me.

Reference:
Pyridine – Wikipedia,
,Pyridine | C5H5N – PubChem