Molecular Biology Experiment Tips

Why measuring loop gain matters for power supply design engineers - and how to do it correctly. When your power system oscillates at 20 kHz after a load step, it's not coincidence. Loop gain measurement shows a phase margin of only 15°. Loop gain is the key indicator of stability in power supply systems. But measuring it correctly requires proper technique: 1. Select the right frequency analyzer settings: - Narrow IF bandwidth reduces noise (but increases sweep time) - Programmable source voltage prevents circuit saturation - Servo control adjusts source amplitude automatically 2. Choose correct injection points: - Impedance looking backward should be much smaller than forward - Keep connection wires short to prevent measurement errors - Include ALL feedback paths (this is crucial) 3. The payoff? Predictable transient response: The relationship is direct: t₁ = 1/(4·fc) With proper phase margin, your circuit responds as designed. 4. Test across all operating conditions: - All output voltage settings - Full output current range - Full input voltage range - Temperature extremes Data shows the impact: In an unstable system with 15° phase margin, output oscillated exactly at the crossover frequency (20 kHz). Small details matter - even your probe reference point affects results. Are you measuring loop gain in your power designs? Or just hoping they'll be stable? Texas Instruments engineers reveal why your power supply measurements don't match simulations. The answer isn't more complex models—it's proper measurement technique at the right injection points with correct reference connections.

Advances in #multiplexed super-resolution microscopy are enabling researchers to understand the cellular complexity and protein function by visualising the intricate interactions and locations of numerous proteins #spatially within a cell. #KeyAdvancements driving this progress: #CyclicImmunofluorescence:These methods, already widely used in tissue imaging, are now being applied to subcellular mapping, providing multidimensional insights into protein localisation. #SuperResolutionMultiplexedImaging techniques: Methods like Exchange-PAINT, FLASH-PAINT, and SUM-PAINT are revolutionising our ability to image multiple proteins at the nanoscale level within cells. SUM-PAINT has even achieved 30-plex super-resolution imaging in neurons. #Value: Information-rich #AtlasProjects and #OpportunityToIntegrate with tissue imaging with nanoscale details of protein architecture in every cell. Key Links: https://lnkd.in/eqEgM7Nn: This research tagged 75% of the yeast proteome with GFP to image protein locations. https://lnkd.in/eHMGpk5D, https://lnkd.in/eHMGpk5D, https://lnkd.in/ePiHn8j4, https://lnkd.in/ePiHn8j4: These studies used CRISPR-based gene targeting for similar efforts in human cell lines. https://lnkd.in/eKsSDYw5: This paper introduced Exchange-PAINT, a pioneering method for multiplexed super-resolution imaging. https://lnkd.in/eHTrdTYv: This article details the development of FLASH-PAINT for multiplexed imaging in cells. https://lnkd.in/eSYkZK5t: This research presents SUM-PAINT, a method for highly multiplexed super-resolution imaging. Got value from this? Share 🔄 #SingleCell #TranslationalResearch #MultiOmics

Attention to pipetting technique is crucial because small handling errors create measurable volume deviations that directly affect reagent concentrations and experimental reproducibility. Maintaining a consistent immersion depth and a vertical angle protects the pressure balance inside the tip, ensuring that the aspirated volume matches the intended setting. - Shallow vertical immersion (~1 cm): minimal pressure disturbance, low error (0.2–0.4%). - Deeper vertical immersion (~3 cm): increased hydrostatic pressure, larger error (0.6–0.8%). - Angled immersion (3–4 cm): unstable air–liquid interface, highest error (1–1.2%). These differences matter because inaccurate pipetting can alter reaction kinetics, reduce consistency between replicates, and compromise data quality in assays such as qPCR, ELISA, and enzyme activity measurements. #PipettingAccuracy #LabPrecision #LiquidHandling #ScientificRigor #Reproducibility #LabBestPractices #MolecularBiology #QualityControl #AccurateMeasurements #LabSkills

◑☞High-Performance Liquid Chromatography (HPLC): HPLC is an advanced analytical technique used for separating, identifying, and quantifying compounds in a mixture. It is widely used in pharmaceuticals, food science, environmental analysis, and biochemistry. ☞Principle of HPLC HPLC operates on the principle of separation based on the interaction between the analyte, the stationary phase, and the mobile phase. Components in a mixture are separated as they pass through the column due to differences in their affinity towards the stationary phase. ☞Key Components of HPLC ➤Mobile Phase ⇨A liquid solvent or a mixture of solvents that carries the sample through the column. ⇨Examples: Water, methanol, acetonitrile, and buffers. ➤Pump ⇨Delivers the mobile phase through the system at high pressure (up to 400 bar). ⇨Maintains consistent flow rates for reproducible results. ➤Injector ⇨Introduces the sample into the HPLC system, either manually or automatically. ⇨Sample volume typically ranges from 1 to 100 µL. ➤Column ⇨Packed with the stationary phase (e.g., silica particles) that separates the analytes. ⇨Types: C18 (Reverse phase), C8, Ion-exchange, Size exclusion. ➤Detector ⇨Identifies and quantifies the separated components. ⇨Common types: UV-Vis, PDA (Photodiode Array), Fluorescence, Refractive Index, and Mass Spectrometry (LC-MS). ➤Data System Software that records, processes, and analyzes the chromatographic data. ☞Basic HPLC Workflow 1.Prepare the sample and mobile phase. 2.Load the sample into the injector. 3.Pump the mobile phase through the system. 4.Separate the analytes in the column. 5.Detect and record the signal with the detector. 6.Analyze the chromatogram using software. ☞Types of HPLC Techniques ➤Normal-Phase HPLC 1.Stationary Phase: Polar (e.g., silica). 2.Mobile Phase: Non-polar (e.g., hexane). ➤Reverse-Phase HPLC 1.Stationary Phase: Non-polar (e.g., C18). 2.Mobile Phase: Polar (e.g., water, methanol). 3.Most commonly used technique. ➤Ion-Exchange HPLC 1.Separates ionic compounds based on their charge. 2.Used for amino acids, proteins, and nucleotides. ➤Size-Exclusion HPLC 1.Separates molecules based on their size. 2.Used for polymers and large biomolecules. ☞Applications of HPLC ➤Pharmaceuticals ~Drug formulation, purity testing, and dissolution studies. ➤Food and Beverage ~Detection of contaminants, preservatives, and nutritional components. ➤Environmental Analysis ~Monitoring pollutants in water, soil, and air. ➤Biochemistry ~Analysis of proteins, peptides, and metabolites. ☞Advantages of HPLC 1.High resolution and sensitivity. 2.Fast and efficient separation. 3.Can handle a wide variety of samples (polar, non-polar, ionic). 4.Quantitative and qualitative analysis in a single run. ☞Disadvantages of HPLC 1.Expensive instrumentation and maintenance. 2.Requires high purity solvents. 3.Complex method development for new samples.

🧪 𝗪𝗵𝗲𝗻 𝘁𝗼 𝗜𝗻𝘁𝗲𝗻𝘁𝗶𝗼𝗻𝗮𝗹𝗹𝘆 𝗠𝗶𝘀𝗺𝗮𝘁𝗰𝗵 𝗖𝗼𝗹𝘂𝗺𝗻 𝗣𝗼𝗹𝗮𝗿𝗶𝘁𝘆 𝘁𝗼 𝗔𝗻𝗮𝗹𝘆𝘁𝗲 𝗣𝗼𝗹𝗮𝗿𝗶𝘁𝘆 In gas chromatography, column selection often follows the rule of thumb: “Like dissolves like.” Match polar analytes with polar stationary phases; use nonpolar columns for nonpolar compounds. It’s a good starting point — and often effective. But sometimes, doing the “wrong” thing on purpose is the right move. 𝗪𝗵𝗲𝗻 “𝗟𝗶𝗸𝗲” 𝗙𝗮𝗶𝗹𝘀 Selectivity isn’t driven by polarity alone. If analytes coelute on a polarity-matched column despite careful optimization, polarity may not be the right differentiator. Intentionally mismatching column polarity introduces orthogonal selectivity. • A nonpolar column may exaggerate boiling point differences between polar analytes or mixed-polarity pairs. • A polar column may resolve nonpolar analytes via dipoles or H-bonding interactions. • Halogenated organics often tail less on nonpolar phases. • Volatile acids and amines often show improved peak shape on nonpolar columns due to reduced H-bonding. 𝗣𝗼𝗹𝗮𝗿𝗶𝘁𝘆 𝘃𝘀. 𝗕𝗼𝗶𝗹𝗶𝗻𝗴 𝗣𝗼𝗶𝗻𝘁 In temperature-programmed GC, two forces dominate separation: volatility and stationary phase interaction. If polarity is similar but boiling points differ, a nonpolar column lets volatility lead. If boiling points are similar but polar moieties differ, a polar column may resolve based on dipole strength or hydrogen bonding. 𝗥𝗲𝗮𝗹-𝗪𝗼𝗿𝗹𝗱 𝗔𝗽𝗽𝗹𝗶𝗰𝗮𝘁𝗶𝗼𝗻𝘀 🔹 Degradant profiling – Resolves polar degradants coeluting with APIs. 🔹 Isomer separation – Positional isomers may resolve only on polar phases. 🔹 Unknown peak ID – Polarity flips can unmask hidden coelutions. 🔹 USP <467> – Polar columns improve resolution of overlapping solvents. 🔹 Multi-API products – Orthogonal selectivity enables single-run assays. 🔹 API + preservative – Mismatched phases balance elution of dissimilar compounds. 🔹 Xylene isomers – Polar phases separate o/m/p isomers cleanly. 🔹 Fragrance analysis – Helps spread semi-volatiles in complex matrices. 𝗔 𝗦𝘁𝗿𝗮𝘁𝗲𝗴𝗶𝗰 𝗟𝗲𝘃𝗲𝗿 𝗶𝗻 𝗠𝗲𝘁𝗵𝗼𝗱 𝗗𝗲𝘃𝗲𝗹𝗼𝗽𝗺𝗲𝗻𝘁 When inlet tweaks and temperature ramps fail to resolve critical peaks, the issue may not be optimization — but limited selectivity. Understanding analyte–stationary phase interactions (polarity, dipole strength, volatility, molecular shape) allows for predictive column selection. Sometimes, disrupting similarity — not reinforcing it — is what unlocks resolution. Mismatch isn’t trial-and-error. It’s rational design. ➡️ 𝗧𝗮𝗸𝗲𝗮𝘄𝗮𝘆: Polarity matching is a guideline, not a law. When resolution stalls, a polarity-opposed column can reveal separations a matched one conceals. It’s not unconventional. It’s smart chromatography. #AnalyticalChemistry #AnalyticalDevelopment #MethodDevelopment #MethodValidation #GasChromatography #ResidualSolvents #SmallMolecules #Pharmaceuticals #Chromatography #analytguru

🧬 Chromatography separates product variants. Native mass spectrometry reveals their molecular identity. For monoclonal antibodies, antibody-drug conjugates and other complex biologics, combining chromatography with native MS connects physicochemical separation with intact molecular composition, higher-order assembly and product heterogeneity. 🧬 Therapeutic antibodies Native MS analyses intact proteins under conditions designed to preserve many non-covalent interactions and higher-order assemblies. For mAbs, bispecific antibodies and Fc-fusion proteins, it can profile: • Intact mass and assembly state • Glycoform and proteoform distributions • Clipping, fragmentation and misassembly • C-terminal lysine retention, glycation and higher-order species More detailed localisation may still require subunit analysis, native top-down MS or peptide mapping. 💊 Antibody–drug conjugates ADCs combine antibody heterogeneity with variation in payload loading, linker stability and conjugation chemistry. Native MS can determine intact ADC mass, average drug-to-antibody ratio and drug-load distribution, while also detecting payload loss, clipping, aggregation and unexpected mass variants. Average DAR, drug-load distribution and positional conjugation heterogeneity are related, but distinct, analytical measurements. 🔬 Connecting chromatography with native MS Depending on the method, chromatography may be coupled directly to native MS or integrated through online buffer exchange, multidimensional separations or offline fraction collection. 🔹️SEC separates by effective hydrodynamic size. SEC–native MS can connect monomer, fragment, dimer and higher-molecular-weight peaks with intact molecular mass. 🔹️IEX separates charge variants. IEX–native MS can associate acidic and basic peaks with attributes such as C-terminal lysine retention, glycation, selected glycoform differences and clipping. 🔹️Affinity MS (Protein A) directly combines selective antibody capture with native MS. In the reported ProA–MS workflow, broad PQA profiling of mAbs and related products was achieved in approximately five minutes, supporting rapid screening and near-real-time process understanding. 🔹️HIC is widely used for ADC drug-load profiling because payload attachment commonly alters hydrophobicity. Direct coupling remains challenging because conventional HIC uses high concentrations of non-volatile salts, so desalting, multidimensional LC or fraction-based MS may be required. 🧪 Summary Chromatography reveals how product populations differ physicochemically. Native MS helps determine their mass, composition, drug loading and assembly state. Together, they move biopharmaceutical characterisation beyond retention-time assignment and towards direct molecular understanding of mAbs, ADCs and other complex therapeutic proteins. #NativeMassSpectrometry #MassSpectrometry #Biopharmaceuticals #MonoclonalAntibodies #AntibodyDrugConjugates

💡Tip clearance is between the tip of a rotating airfoil and a stationary part. 💡Since the turbine rotor is a rotating component, and the a stationary component, the gap should be there to facilitate the movement of the blade. This gap (the radial distance between the tip of the turbine blade and with integral blade shroud) is called turbine blade tip clearance. 💡Feeler gauges are used to measure rotor clearances in gas turbines, specifically the gap between the rotating blades and the surrounding casing. These clearances are crucial for maintaining optimal turbine efficiency and preventing damage. 💡 Accurate measurement of these clearances is necessary during maintenance and assembly. 💡Here's a more detailed explanation: ✅Purpose: Gas turbine rotors have narrow clearances between the rotating blades and the stationary casing. These clearances are critical for efficiency; too much clearance reduces efficiency, while too little can lead to blade rubbing and potential damage. ✅Feeler Gauge Use: Feeler gauges, which are thin strips of metal with calibrated thicknesses, are used to measure these clearances. The gauge is inserted into the gap between the blade and the casing, and the thickness of the gauge that just fits is recorded. ✅Measurement Process: The process involves removing the upper half of the turbine casing to access the rotor and blades. The feeler gauge is carefully inserted at multiple points around the circumference of the rotor. It's crucial to simulate the engine's running conditions (e.g., thermal expansion) during measurement. This can involve lifting the rotor slightly to account for its position under load. ✅Importance of Accurate Measurement: Precise clearance measurements are essential for ensuring the turbine operates at its optimal performance and for preventing blade rubs and damage. Variations in clearance can indicate potential issues, such as blade wear or casing deformation. ✅Other Measurement Methods: While feeler gauges are common, other methods like capacitive or inductive sensors are also used, especially for continuous monitoring of clearances during operation. Laser-based systems can also be employed, projecting a laser beam onto the blades and measuring the reflected beam's position.

🌟 Welcome back everyone! Continuing our Instrumentation & Control series — in the previous post, we introduced Flow Measurement, its importance, and the main measurement principles. Today, we begin the detailed discussion of flow measurement technologies, starting with the most widely used and classical method: 💧 Differential Pressure (DP) Flow Measurement This method has been used for decades and remains a cornerstone in industrial flow measurement due to its reliability, standardization, and wide acceptance across industries. This method is widely used because it is: ✔ Proven ✔ Standardized ✔ Accepted in almost all industries ✔ Suitable for high pressure & high temperature services 1️⃣ Basic Principle of DP Flow Measurement DP flow measurement is based on Bernoulli’s principle: When a fluid flows through a restriction, its velocity increases and pressure decreases. The flow rate is proportional to: 📌 Square root of differential pressure (ΔP) 2️⃣ Primary Flow Elements (The Heart of DP Flow) The primary element creates the pressure drop. 🔹 Orifice Plate (Most Common) ✔ Simple & low cost ✔ Easy to install ✔ Widely standardized (ISO / API) Types: Concentric orifice (clean fluids) Eccentric orifice (liquids with solids) Segmental orifice (slurries) Limitations: 🚫 Permanent pressure loss 🚫 Sensitive to installation 🔹 Venturi Tube ✔ High accuracy ✔ Very low pressure loss ✔ Good for dirty services Limitations: 🚫 High cost 🚫 Large size 🔹 Flow Nozzle ✔ Suitable for high velocity & steam ✔ More robust than orifice 3️⃣ Orifice Plate Installation (Very Important) ✔ Upstream & downstream straight pipe lengths ✔ Correct orientation ✔ Sharp edge condition ✔ Correct bore calculation ✔ Flow direction marking ⚠️ Even small installation errors can cause large flow errors. 4️⃣ DP Transmitter Role The DP transmitter: Measures pressure difference (High side – Low side) Converts it into 4–20 mA Sends signal to DCS/PLC The control system: ✔ Extracts square root ✔ Calculates actual flow 5️⃣ Typical DP Flow Applications 🏭 Steam flow 🏭 Fuel gas 🏭 Feedwater 🏭 Process liquids 🏭 Air & compressed gas 6️⃣ Common Installation Mistakes (Construction Phase) 🚫 Wrong tapping location 🚫 No straight length 🚫 Impulse lines not sloped 🚫 Wrong transmitter elevation 🚫 Mixing HP & LP lines 📌 Key Engineering Note DP flow measurement accuracy depends on: Primary element design Installation quality Correct impulse line routing Proper transmitter selection 🔜 Coming Next In the next post, we’ll deep dive into Orifice Plates: ✔ Design ✔ Tapping types ✔ Installation drawings ✔ Field mistakes 💬 Discussion Question: What is the most common DP flow installation mistake you’ve seen in the field? ✍️ Eng. Ahmed Elwan

📏 Quality Inspection Instruments – The Foundation of Manufacturing Excellence 📏 In the manufacturing industry, product quality is not achieved by inspection alone—it begins with accurate measurement. Understanding the correct use of measuring instruments, their least count, calibration requirements, and applications is essential for every Quality Engineer, Production Engineer, and Manufacturing Professional. From Steel Rule, Vernier Caliper, Micrometer, Dial Indicator, Height Gauge, Plug Gauge, Ring Gauge, CMM, VMM, and Surface Roughness Tester, each instrument plays a critical role in ensuring dimensional accuracy, process capability, and customer satisfaction. 🔹 Key Takeaways: ✅ Select the right instrument based on tolerance requirements. ✅ Understand the least count and measurement accuracy. ✅ Ensure periodic calibration and traceability to national/international standards. ✅ Follow proper measurement techniques to eliminate human error. ✅ Focus on accuracy and precision for reliable inspection results. ✅ Use advanced systems like CMM and VMM for critical dimensions and complex geometries. Manufacturing Example: If a shaft diameter specification is Ø25 ±0.02 mm, measuring it with a steel rule is not appropriate. A calibrated micrometer with a least count of 0.01 mm or better should be used to ensure accurate inspection and compliance with customer requirements. Quality is built on data, and data is built on accurate measurements. A strong understanding of metrology not only improves product quality but also reduces rejection, rework, customer complaints, and overall Cost of Poor Quality (COPQ). 📌 "What gets measured accurately gets controlled effectively." I have prepared this handwritten reference sheet to help quality and manufacturing professionals quickly understand the most commonly used inspection instruments and their applications. Prepared By: Rajeshwar #QualityEngineering #Metrology #MeasurementSystem #Calibration #Manufacturing #AutomotiveIndustry #IATF16949 #QualityControl #QualityAssurance #Inspection #CMM #VMM #Micrometer #VernierCaliper #DialGauge #SPC #MSA #LeanManufacturing #ContinuousImprovement #RajeshwarGholap #QualityManagement #EngineeringExcellence